Vitamin D for COVID-19: real-time meta analysis of 156 studies

https://vdmeta.com/

•Statistically significant improvements are seen in treatment studies for mortality, ventilation, ICU admission, hospitalization, and cases. 30 studies from 27 independent teams in 12 different countries show statistically significant improvements in isolation (22 for the most serious outcome).

•Random effects meta-analysis with pooled effects using the most serious outcome reported shows 81% [53‑92%] and 43% [35‑51%] improvement for early treatment and for all studies. Results are similar after restriction to 53 peer-reviewed studies: 77% [45‑90%] and 44% [35‑51%], and for the 33 mortality results: 76% [37‑91%] and 47% [33‑59%].

•Late stage treatment with calcifediol/calcitriol shows greater improvement compared to cholecalciferol: 78% [67‑85%] vs. 43% [24‑58%].

•Sufficiency studies show a strong association between vitamin D sufficiency and outcomes. Meta analysis of the 98 studies using the most serious outcome reported shows 57% [50‑62%] improvement.

•While many treatments have some level of efficacy, they do not replace vaccines and other measures to avoid infection. Only 12% of vitamin D treatment studies show zero events in the treatment arm.

•Elimination of COVID-19 is a race against viral evolution. No treatment, vaccine, or intervention is 100% available and effective for all current and future variants. All practical, effective, and safe means should be used. Not doing so increases the risk of COVID-19 becoming endemic; and increases mortality, morbidity, and collateral damage.

•All data to reproduce this paper and the sources are in the appendix.

	Improvement	Studies	Authors	Patients
Treatment RCTs	55% [26‑72%]	10	90	834
Treatment studies	43% [35‑51%]	58	581	122,873
Cholecalciferol treatment	43% [33‑51%]	49	470	114,530
Calcifediol/calcitriol treatment	53% [26‑71%]	9	111	8,343
Treatment mortality	47% [33‑59%]	33	299	29,359
Sufficiency studies	57% [50‑62%]	98	807	197,397

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Figure 1. A. Random effects meta-analysis of treatment studies. This plot shows pooled effects, analysis for individual outcomes is below, and more details on pooled effects can be found in the heterogeneity section. Effect extraction is pre-specified, using the most serious outcome reported. Simplified dosages are shown for comparison, these are the total dose in the first five days for treatment, and the monthly dose for prophylaxis. Calcifediol, calcitriol, and paricalcitol treatment are indicated with (c), (t), and (p). For details of effect extraction and full dosage information see the appendix. B. Scatter plot showing the distribution of effects reported in serum level analysis (sufficiency) studies and treatment studies (the vertical lines and shaded boxes show the median and interquartile range). C and D. Chronological history of all reported effects for treatment studies and sufficiency studies.

Introduction

We analyze all significant studies regarding vitamin D and COVID-19. Search methods, inclusion criteria, effect extraction criteria (more serious outcomes have priority), all individual study data, PRISMA answers, and statistical methods are detailed in Appendix 1. We present random-effects meta-analysis results for studies analyzing outcomes based on sufficiency, for all treatment studies, for mortality results only, and for treatment studies within each treatment stage.

Vitamin D.

Vitamin D undergoes two conversion steps before reaching the biologically active form as shown in Figure 2. The first step is conversion to calcidiol, or 25(OH)D, in the liver. The second is conversion to calcitriol, or 1,25(OH)2D, which occurs in the kidneys, the immune system, and elsewhere. Calcitriol is the active, steroid-hormone form of vitamin D, which binds with vitamin D receptors found in most cells in the body. Vitamin D was first identified in relation to bone health, but is now known to have multiple functions, including an important role in the immune system [Carlberg, Martens]. For example, [Quraishi] show a strong association between pre-operative vitamin D levels and hospital-acquired infections, as shown in Figure 3. There is a significant delay involved in the conversion from cholecalciferol, therefore calcifediol (calcidiol) or calcitriol may be preferable for treatment.

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Figure 2. Simplified view of vitamin D sources and conversion.

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Figure 3. Risk of hospital-acquired infections as a function of pre-operative vitamin D levels, from [Quraishi].

Sufficiency.

Many vitamin D studies analyze outcomes based on serum vitamin D levels which may be maintained via sun exposure, diet, or supplementation. We refer to these studies as sufficiency studies, as they typically present outcomes based on vitamin D sufficiency. These studies do not establish a causal link between vitamin D and outcomes. In general, low vitamin D levels are correlated with many other factors that may influence COVID-19 susceptibility and severity. Therefore, beneficial effects found in these studies may be due to factors other than vitamin D. On the other hand, if vitamin D is causally linked to the observed benefits, it is possible that adjustments for correlated factors could obscure this relationship. COVID-19 disease may also affect vitamin D levels [Silva], suggesting additional caution in interpreting results for studies where the vitamin D levels are measured during the disease. For these reasons, we analyze sufficiency studies separately from treatment studies. We include all sufficiency studies that provide a comparison between two groups with low and high levels. A few studies only provide results as a function of change in vitamin D levels [Butler-Laporte, Raisi-Estabragh], which may not be indicative of results for deficiency/insufficiency versus sufficiency (increasing already sufficient levels may be less useful for example). A few studies show the average vitamin D level for patients in different groups [Al-Daghri, Chodick, D'Avolio, Desai, Ersöz, Kerget, Mardani, Vassiliou], all of which show lower D levels for worse outcomes. Other studies analyze vitamin D status and outcomes in geographic regions [Jayawardena, Marik, Papadimitriou, Rafailia, Rhodes, Sooriyaarachchi, Walrand, Yadav], all finding worse outcomes to be more likely with lower D levels.

Sufficiency studies vary widely in terms of when vitamin D levels were measured, the cutoff level used, and the population analyzed (for example studies with hospitalized patients exclude the effect of vitamin D on the risk of hospitalization). We do not analyze sufficiency studies in more detail because there are many controlled treatment studies that provide better information on the use of vitamin D as a treatment for COVID-19. A more detailed analysis of sufficiency studies can be found in [Chiodini].

Treatment.

For studies regarding treatment with vitamin D, we distinguish three stages as shown in Figure 4. Prophylaxis refers to regularly taking vitamin D before being infected in order to minimize the severity of infection. Due to the mechanism of action, vitamin D is unlikely to completely prevent infection, although it may prevent infection from reaching a level detectable by PCR. Early Treatment refers to treatment immediately or soon after symptoms appear, while Late Treatment refers to more delayed treatment.

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Figure 4. Treatment stages.

Results

Figure 1 shows the effects reported in sufficiency studies and treatment studies. Figure 5 and 6 show results by treatment stage. Figure 7 shows a forest plot for random effects meta-analysis of sufficiency studies, while Figure 8, 9, 10, 11, 12, 13, 14, 15, and 16 show forest plots for all treatment studies with pooled effects, cholecalciferol studies, calcifediol/calcitriol studies, for studies reporting mortality, mechanical ventilation, ICU admission, hospitalization, and case results only. Table 1 summarizes the results.

Study type	Number of studies reporting positive results	Total number of studies	Percentage of studies reporting positive results	Random effects meta-analysis results
Analysis of outcomes based on sufficiency	92	98	93.9%	57% improvement RR 0.43 [0.38‑0.50] p < 0.0001
Early treatment	6	6	100%	81% improvement RR 0.19 [0.08‑0.47] p = 0.00032
Late treatment	19	21	90.5%	54% improvement RR 0.46 [0.33‑0.63] p < 0.0001
Prophylaxis	25	31	80.6%	35% improvement RR 0.65 [0.56‑0.76] p < 0.0001
All treatment studies	50	58	86.2%	43% improvement RR 0.57 [0.49‑0.65] p < 0.0001

Table 1. Results.

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Figure 5. Results by treatment stage.

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Figure 6. Results by treatment stage.

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Figure 11. Random effects meta-analysis for calcifediol/calcitriol treatment studies. Effect extraction is pre-specified, using the most serious outcome reported, see the appendix for details.

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Figure 12. Random effects meta-analysis for treatment mortality results only.

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Figure 13. Random effects meta-analysis for treatment mechanical ventilation results only.

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Figure 14. Random effects meta-analysis for treatment ICU admission results only.

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Figure 15. Random effects meta-analysis for treatment hospitalization results only.

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Figure 16. Random effects meta-analysis for treatment COVID-19 case results only.

Exclusions

To avoid bias in the selection of studies, we include all studies in the main analysis, with the exception of [Espitia-Hernandez]. This study uses a combined protocol with another medication that shows high effectiveness when used alone. Authors report on viral clearance, showing 100% clearance with treatment and 0% for the control group. Based on the known mechanisms of action, the combined medication is likely to contribute more to the improvement.

Here we show the results after excluding studies with critical issues.

[Murai] is a very late stage study (mean 10 days from symptom onset, with 90% on oxygen at baseline), with poorly matched arms in terms of gender, ethnicity, hypertension, diabetes, and baseline ventilation, all of which favor the control group. Further, this study uses cholecalciferol, which may be especially poorly suited for such a late stage.

The studies excluded are as follows, and the resulting forest plot is shown in Figure 17.

[Abdulateef], unadjusted results with no group details.

[Asimi], excessive unadjusted differences between groups.

[Assiri], unadjusted results with no group details.

[Campi], significant unadjusted differences between groups.

[Güven], very late stage, ICU patients.

[Holt], significant unadjusted confounding possible.

[Krishnan], unadjusted results with no group details.

[Leal], combined treatments may contribute more to the effect seen.

[Lázaro], very few events, unadjusted results with no group details, minimal details provided.

[Mohseni], unadjusted results with no group details.

[Murai], very late stage, >50% on oxygen/ventilation at baseline.

[Pecina], unadjusted results with no group details.

Randomized Controlled Trials (RCTs)

Results restricted to Randomized Controlled Trials (RCTs), after exclusions, and after restriction to mortality results are shown in Figure 18, 19, and 20.

RCTs have a bias against finding an effect for interventions that are widely available — patients that believe they need the intervention are more likely to decline participation and take the intervention. This is illustrated with the extreme example of an RCT showing no significant differences for use of a parachute when jumping from a plane [Yeh]. RCTs for vitamin D are more likely to enroll low-risk participants that do not need treatment to recover, making the results less applicable to clinical practice. This bias is likely to be greater for well-known treatments such as vitamin D. Note that this bias does not apply to the typical pharmaceutical trial of a new drug that is otherwise unavailable.

Evidence shows that non-RCT trials can also provide reliable results. [Concato] find that well-designed observational studies do not systematically overestimate the magnitude of the effects of treatment compared to RCTs. [Anglemyer] summarized reviews comparing RCTs to observational studies and found little evidence for significant differences in effect estimates. [Lee] shows that only 14% of the guidelines of the Infectious Diseases Society of America were based on RCTs. Evaluation of studies relies on an understanding of the study and potential biases. Limitations in an RCT can outweigh the benefits, for example excessive dosages, excessive treatment delays, or Internet survey bias could have a greater effect on results. Ethical issues may also prevent running RCTs for known effective treatments. For more on issues with RCTs see [Deaton, Nichol].

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Figure 19. Random effects meta-analysis for RCTs after exclusions. Effect extraction is pre-specified, using the most serious outcome reported, see the appendix for details.

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Figure 20. Random effects meta-analysis for RCT mortality results after exclusions.

Heterogeneity

Heterogeneity in COVID-19 studies arises from many factors including:

Treatment delay.

The time between infection or the onset of symptoms and treatment may critically affect how well a treatment works. For example a medication may be very effective when used early but may not be effective in late stage disease, and may even be harmful. Figure 21 shows an example where efficacy declines as a function of treatment delay. Other medications might be beneficial for late stage complications, while early use may not be effective or may even be harmful.

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Figure 21. Effectiveness may depend critically on treatment delay.

Patient demographics.

Details of the patient population including age and comorbidities may critically affect how well a treatment works. For example, many COVID-19 studies with relatively young low-comorbidity patients show all patients recovering quickly with or without treatment. In such cases, there is little room for an effective treatment to improve results.

Effect measured.

Efficacy may differ significantly depending on the effect measured, for example a treatment may be very effective at reducing mortality, but less effective at minimizing cases or hospitalization. Or a treatment may have no effect on viral clearance while still being effective at reducing mortality.

Variants.

There are thousands of different variants of SARS-CoV-2 and efficacy may depend critically on the distribution of variants encountered by the patients in a study.

Regimen.

Effectiveness may depend strongly on the dosage, treatment regimen, and the form of vitamin D used (cholecalciferol, calcifediol, or calcitriol).

Treatments.

The use of other treatments may significantly affect outcomes, including anything from other supplements and medications, or other kinds of treatment such as prone positioning.

The distribution of studies will alter the outcome of a meta analysis. Consider a simplified example where everything is equal except for the treatment delay, and effectiveness decreases to zero or below with increasing delay. If there are many studies using very late treatment, the outcome may be negative, even though the treatment may be very effective when used earlier.

In general, by combining heterogeneous studies, as all meta analyses do, we run the risk of obscuring an effect by including studies where the treatment is less effective, not effective, or harmful.

When including studies where a treatment is less effective we expect the estimated effect size to be lower than that for the optimal case. We do not a priori expect that pooling all studies will create a positive result for an effective treatment. Looking at all studies is valuable for providing an overview of all research, and important to avoid cherry-picking, but the resulting estimate does not apply to specific cases such as early treatment in high-risk populations with a specific form and dosage of vitamin D.

Vitamin D studies vary widely in all the factors above, which makes the consistently positive results even more remarkable. A failure to detect an association after combining heterogeneous studies does not mean the treatment is not effective (it may only work in certain cases), however the reverse is not true — an identified association is valid, although the magnitude of the effect may be larger for more optimal cases, and lower for less optimal cases. While we present results for all studies in this paper, the individual outcome, form of vitamin D, and treatment time analyses are more relevant for specific use cases.

Discussion

Typical meta analyses involve subjective selection criteria, effect extraction rules, and study bias evaluation, which can be used to bias results towards a specific outcome. In order to avoid bias we include all studies and use a pre-specified method to extract results from all studies. This provides an overview of all research.

For sufficiency studies, different studies use different levels as the threshold of sufficiency, and some studies measure risk only within hospitalized patients, which excludes the risk of a serious enough case to be hospitalized, however 92 of 98 studies present positive effects.

50 of 58 treatment studies report positive effects. Studies vary significantly in terms of treatment delay, treatment regimen, patients characteristics, and (for the pooled effects analysis) outcomes, as reflected in the high degree of heterogeneity. However treatment consistently shows a significant benefit. The treatment studies not showing positive effects are mostly prophylaxis studies with unknown dosages. The only non-prophylaxis studies reporting negative effects are a small unadjusted retrospective [Assiri], and [Murai] which is a very late stage study using cholecalciferol. This result also has very low statistical significance due to the small number of events, and the other reported outcomes of ventilation and ICU admission, which have slightly more events and higher confidence, show benefits for vitamin D. Calcifediol or calcitriol, which avoids several days delay in conversion, may be more successful, especially with this very late stage usage.

Conclusion

Random effects meta-analysis with pooled effects using the most serious outcome reported shows 81% [53‑92%] and 43% [35‑51%] improvement for early treatment and for all studies. Results are similar after restriction to 53 peer-reviewed studies: 77% [45‑90%] and 44% [35‑51%], and for the 33 mortality results: 76% [37‑91%] and 47% [33‑59%].

Statistically significant improvements are seen in treatment studies for mortality, ventilation, ICU admission, hospitalization, and cases. 30 studies from 27 independent teams in 12 different countries show statistically significant improvements in isolation (22 for the most serious outcome).

Late stage treatment with calcifediol/calcitriol shows greater improvement compared to cholecalciferol: 78% [67‑85%] vs. 43% [24‑58%].

Responses

GMK response.

An influential anti-treatment Twitter personality, journalist, and epidemiologist is known for being against many COVID-19 treatments including vitamin D. Of the 58 treatment studies, author suggests only one trial is worth looking at [Murai]. This makes it easy to examine potential bias. [Murai] is a small trial providing no statistically significant effects (mortality p = 0.43, other outcomes are positive while also not significant). Author acknowledges that the trial is too small for a conclusion. More importantly, this trial provides no information about whether vitamin D reduces the risk of a serious COVID-19 case, because the patients in this trial already had a serious COVID-19 case (90% already on oxygen treatment at baseline). Author does not mention this. The trial also has poorly matched arms in terms of gender, ethnicity, hypertension, diabetes, and baseline ventilation, all favoring the control group. Further, this study uses an inappropriate form of vitamin D — cholecalciferol. In reality physicians would use calcifediol or calcitriol with late stage treatment, because they avoid a very long delay for conversion. We are unaware of a reason to use cholecalciferol in this case (other than to produce a null result). In summary, author's chosen study is the study providing the least useful information from the 58 studies to date, suggesting biased analysis.

Revisions

This paper is data driven, all graphs and numbers are dynamically generated. We will update the paper as new studies are released or with any corrections. Please submit updates and corrections at the bottom of this page.Please submit updates and corrections at https://vdmeta.com/.

1/5: We added [Pepkowitz].

1/3/2022: We added [Efird].

12/26: We added [Abdulateef].

12/21: We added [Beigmohammadi, Sainz-Amo].

12/20: We added [Galaznik].

12/17: We added [Seven].

12/16: We added [Parra-Ortega].

12/14: We added [Putra].

12/9: We added analysis of the number of independent research groups reporting statistically significant positive results.

12/7: We added [Ma].

12/5: We added [Asgari].

12/3: We updated [Loucera] to the journal version.

12/3: We added [Fatemi].

12/3: We added [Kaur].

11/22: Added discussion related to sufficiency studies.

11/14: We added [Gönen].

11/12: We added [Asghar].

11/7: We added [Holt].

11/3: We added [Atanasovska].

11/2: We added [Al-Salman, Eden].

11/1: We updated [Golabi] to the journal version.

10/31: We added [Assiri, Bianconi, Leal].

10/30: We added [Campi, Gaudio].

10/29: We added discussion of GMK's vitamin D analysis.

10/27: We added [Hurst, Lázaro].

10/19: We added [Jimenez].

10/19: We added [Sinaci, Zelzer].

10/18: We added [Mohseni].

10/18: We added [Basaran, Dudley].

10/16: We added a summary plot for all results.

10/15: We added [Ramirez-Sandoval].

10/15: We added [Maghbooli (B)].

10/14: We added [Arroyo-Díaz, Burahee] and analysis of treatment mechanical ventilation, ICU admission, and hospitalization results.

9/28: We added [Yildiz].

9/27: We added [Derakhshanian].

9/22: We added [Bagheri].

9/14: We added [Ribeiro].

9/14: We updated [Vasheghani (B)] to the journal version of the article.

9/14: We added [Elamir].

9/10: We added [Tomasa-Irriguible].

9/7: We added [Karonova, Pecina].

9/6: We added [Soliman].

9/1: We added [Golabi].

8/23: We corrected [Jain] to include the mortality outcome.

8/15: We added [Nimavat].

8/13: We added [di Filippo] and updated [Louca] to the journal version of the article.

8/12: We added [Alpcan].

8/10: We added discussion of the immune system and vitamin D.

8/2: We added [Matin].

8/1: We added [Pimental].

7/28: We added [Israel (B)].

7/27: We added [Cozier].

7/26: We added [Güven].

7/25: We added [Asimi].

7/24: We added [Orchard].

7/21: We added [Savitri].

7/19: We added [Oristrell].

7/11: We added [Krishnan].

6/25: We added [Cereda (B)].

6/19: We added [Jude].

6/16: We added [Campi].

6/12: We added [Levitus].

6/11: We updated [Oristrell (B)] to the journal version.

6/9: We added [Fasano].

6/8: We updated [Nogués] to the journal version.

6/7: We added [Diaz-Curiel, Dror].

5/29: We added [Sánchez-Zuno (B)].

5/22: We added analysis restricted to cholecalciferol studies.

5/21: We added [Alcala-Diaz, Li].

5/20: We updated [Lakkireddy] to the journal version.

5/19: We added [AlSafar].

5/10: We added additional information in the abstract.

5/9: We clarified terminology for prophylaxis and added discussion of heterogeneity.

5/8: We added analysis for treatment studies restricted to peer-reviewed articles.

4/30: We added [Loucera].

4/29: We corrected the treatment group counts for the early treatment group in [Annweiler] (there was no change in the relative risk).

4/24: We added analysis restricted to RCT studies and to calcifediol/calcitriol studies. We have excluded [Espitia-Hernandez] in the treatment analysis because they use a combined protocol with another medication that shows high effectiveness when used alone.

4/14: We added [Blanch-Rubió].

4/13: We added [Lohia, Oristrell (B)].

4/12: We added [Barassi].

4/10: We added [Szeto].

4/9: We added [Ünsal].

4/5: We added [Bayramoğlu, Livingston].

4/4: We added event counts to the forest plots.

3/31: We added [Mendy].

3/30: We added [Macaya].

3/29: We added [Im].

3/28: We added [Freitas].

3/22: We added [Meltzer].

3/15: We added [Vanegas-Cedillo].

3/14: We added [Cereda].

3/12: We added [Charoenngam].

3/10: We added [Mazziotti].

3/6: We added [Ricci].

2/26: We added [Lakkireddy].

2/25: We added [Sulli (B)].

2/20: We added [Gavioli].

2/20: We added [Infante].

2/18: [Murai] was updated to the journal version of the paper.

2/17: We corrected an error in the effect extraction for [Angelidi], and we added treatment case and viral clearance forest plots.

2/16: We added [Susianti].

2/10: We added [Nogués].

2/10: We added [Karonova (B)].

2/9: We added [Karahan].

2/7: We added [Li (B)].

2/5: We added [Yılmaz].

1/31: We added [Demir].

1/30: We added [Ma (B)].

1/22: We added [Giannini].

1/21: We added [Bennouar].

1/19: We added [Amin].

1/18: We added [Vasheghani (B)].

1/16: We moved the analysis with exclusions to the main text, and added additional commentary.

1/15: We added the effect measured for each study in the forest plots.

1/10: We added [Angelidi].

1/7: We added direct links to the study details in the chronological plots.

1/5: We added direct links to the study details in the forest plots.

1/2/2021: We added dosage information and we added the number of patients to the forest plots.

12/31: We added additional details about the studies in the appendix.

12/28: We added [Jevalikar].

12/27: We added the total number of authors and patients.

12/23: We added [Cangiano].

12/17/2020: Initial revision.

Appendix 1. Methods and Study Results

We performed ongoing searches of PubMed, medRxiv, ClinicalTrials.gov, The Cochrane Library, Google Scholar, Collabovid, Research Square, ScienceDirect, Oxford University Press, the reference lists of other studies and meta-analyses, and submissions to the site c19vitamind.com. Search terms were vitamin D, cholecalciferol, and calcitriol, and COVID-19 or SARS-CoV-2. Automated searches are performed every hour with notification of new matches. All studies that report a result for vitamin D treatment of COVID-19 patients compared to a control group, and all studies comparing COVID-19 outcomes in groups of patients with low and high vitamin D levels are included. A few studies only provide results as a function of change in vitamin D levels, which may not be indicative of results for deficiency/insufficiency versus sufficiency (if levels are already sufficient then further increase may be less useful). This is a living analysis and is updated regularly.

We extracted effect sizes and associated data from all studies. If studies report multiple kinds of effects then the most serious outcome is used in pooled analysis, while other outcomes are included in the outcome specific analyses. For example, if effects for mortality and cases are both reported, the effect for mortality is used, this may be different to the effect that a study focused on. If symptomatic results are reported at multiple times, we used the latest time, for example if mortality results are provided at 14 days and 28 days, the results at 28 days are used. Mortality alone is preferred over combined outcomes. Outcomes with zero events in both arms were not used (the next most serious outcome is used — no studies were excluded). For example, in low-risk populations with no mortality, a reduction in mortality with treatment is not possible, however a reduction in hospitalization, for example, is still valuable. Clinical outcome is considered more important than PCR testing status. When basically all patients recover in both treatment and control groups, preference for viral clearance and recovery is given to results mid-recovery where available (after most or all patients have recovered there is no room for an effective treatment to do better). If only individual symptom data is available, the most serious symptom has priority, for example difficulty breathing or low SpO₂ is more important than cough. When results provide an odds ratio, we computed the relative risk when possible, or converted to a relative risk according to [Zhang]. Reported confidence intervals and p-values were used when available, using adjusted values when provided. If multiple types of adjustments are reported including propensity score matching (PSM), the PSM results are used. When needed, conversion between reported p-values and confidence intervals followed [Altman, Altman (B)], and Fisher's exact test was used to calculate p-values for event data. If continuity correction for zero values is required, we use the reciprocal of the opposite arm with the sum of the correction factors equal to 1 [Sweeting]. Results are expressed with RR < 1.0 favoring treatment, and using the risk of a negative outcome when applicable (for example, the risk of death rather than the risk of survival). If studies only report relative continuous values such as relative times, the ratio of the time for the treatment group versus the time for the control group is used. Calculations are done in Python (3.9.9) with scipy (1.7.3), pythonmeta (1.26), numpy (1.21.4), statsmodels (0.14.0), and plotly (5.4.0).

Forest plots are computed using PythonMeta [Deng] with the DerSimonian and Laird random effects model (the fixed effect assumption is not plausible in this case) and inverse variance weighting. Forest plots show simplified dosages for comparison, these are the total dose in the first five days for treatment, and the monthly dose for prophylaxis. Calcifediol, calcitriol, and paricalcitol treatment are indicated with (c), (t), and (p). For full dosage details see below.

We received no funding, this research is done in our spare time. We have no affiliations with any pharmaceutical companies or political parties.

We have classified studies as early treatment if most patients are not already at a severe stage at the time of treatment, and treatment started within 5 days of the onset of symptoms. If studies contain a mix of early treatment and late treatment patients, we consider the treatment time of patients contributing most to the events (for example, consider a study where most patients are treated early but late treatment patients are included, and all mortality events were observed with late treatment patients).

A summary of study results is below. Please submit updates and corrections at the bottom of this page.

A summary of study results is below. Please submit updates and corrections at https://vdmeta.com/.

Analysis of outcomes based on sufficiency

Effect extraction follows pre-specified rules as detailed above and gives priority to more serious outcomes. Only the first (most serious) outcome is used in pooled analysis, which may differ from the effect a paper focuses on. Other outcomes are used in outcome specific analyses.

[Abdollahi], 12/12/2020, retrospective, Iran, Middle East, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of case, 53.9% lower, RR 0.46, p = 0.001, high D levels 108, low D levels 294, >30ng/ml.
[Abrishami], 10/30/2020, retrospective, Iran, Middle East, peer-reviewed, mean age 55.2, 7 authors. Submit Corrections or Updates.	risk of death, 75.9% lower, RR 0.24, p = 0.04, high D levels (≥25ng/mL) 3 of 47 (6.4%), low D levels (<25ng/mL) 9 of 26 (34.6%), NNT 3.5, adjusted per study, Cox model 2.
[Afaghi], 10/12/2021, retrospective, Iran, Middle East, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of death, 55.0% lower, RR 0.45, p = 0.002, high D levels 97 of 537 (18.1%), low D levels 51 of 109 (46.8%), NNT 3.5, adjusted per study, odds ratio converted to relative risk, >20ng/mL, multivariate.
	risk of mechanical ventilation, 55.9% lower, RR 0.44, p < 0.001, high D levels 89 of 537 (16.6%), low D levels 41 of 109 (37.6%), NNT 4.8, >20ng/mL, unadjusted.
	risk of ICU admission, 34.1% lower, RR 0.66, p < 0.001, high D levels 211 of 537 (39.3%), low D levels 65 of 109 (59.6%), NNT 4.9, >20ng/mL, unadjusted.
[Al-Salman], 7/29/2021, retrospective, Bahrain, Middle East, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of ICU admission, 44.4% lower, RR 0.56, p = 0.03, high D levels (≥50nmol/L) 113, low D levels (<50nmol/L) 337, multinomial regression, RR approximated with OR.
[Alguwaihes], 12/5/2020, retrospective, Saudi Arabia, Middle East, peer-reviewed, 10 authors. Submit Corrections or Updates.	risk of death, 85.7% lower, RR 0.14, p = 0.007, high D levels 111, low D levels 328, >12.5 nmol/L.
[Alpcan], 8/10/2021, retrospective, Turkey, Europe, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of case, 73.0% lower, RR 0.27, p < 0.001, high D levels 42 of 75 (56.0%) cases, 66 of 80 (82.5%) controls, NNT 3.2, case control OR, >20ng/mL.
[AlSafar], 5/19/2021, retrospective, United Arab Emirates, Middle East, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 59.3% lower, RR 0.41, p = 0.05, high D levels 16 of 337 (4.7%), low D levels 10 of 127 (7.9%), NNT 32, adjusted per study, odds ratio converted to relative risk, >=12ng/mL.
	risk of severe case, 33.2% lower, RR 0.67, p = 0.005, high D levels 337, low D levels 127, adjusted per study, odds ratio converted to relative risk, >=12ng/mL.
[Amin], 1/7/2021, retrospective, population-based cohort, United Kingdom, Europe, peer-reviewed, 2 authors. Submit Corrections or Updates.	COVID-19 severity, 32.3% higher, RR 1.32, p = 0.20, high D levels 140,898, low D levels 35,079, odds ratio converted to relative risk, >=50nmol/L vs. <25nmol/L, MR Egger, baseline risk approximated with overall risk.
	risk of case, 7.6% higher, RR 1.08, p = 0.14, high D levels 140,898, low D levels 35,079, odds ratio converted to relative risk, >=50nmol/L vs. <25nmol/L, MR Egger, baseline risk approximated with overall risk.
[Angelidi], 1/9/2021, retrospective, USA, North America, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 88.0% lower, RR 0.12, p = 0.01, high D levels 6 of 65 (9.2%), low D levels 20 of 79 (25.3%), NNT 6.2, adjusted per study, >30ng/mL, supplementary table 2, multivariable logistic regression model 5.
[Asgari], 11/21/2021, retrospective, Iran, Middle East, peer-reviewed, 6 authors, 21 May, 2020 - 4 September, 2020. Submit Corrections or Updates.	risk of death, 72.5% lower, RR 0.27, p = 0.03, adjusted per study, RR approximated with OR.
	risk of progression, 65.6% lower, RR 0.34, p = 0.02, adjusted per study, RR approximated with OR.
[Asghar], 11/10/2021, retrospective, Pakistan, South Asia, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 53.1% lower, RR 0.47, p = 0.05, high D levels (≥10ng/mL) 73, low D levels (<10ng/mL) 18, multivariate Cox regression.
	risk of mechanical ventilation, 19.4% lower, RR 0.81, p = 0.32, high D levels (≥10ng/mL) 5 of 73 (6.8%), low D levels (<10ng/mL) 6 of 18 (33.3%), NNT 3.8, adjusted per study, multivariate Cox regression.
	risk of ICU admission, 32.9% lower, RR 0.67, p = 0.54, high D levels (≥10ng/mL) 73, low D levels (<10ng/mL) 18, multivariate Cox regression.
[Atanasovska], 11/2/2021, retrospective, North Macedonia, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 40.7% lower, RR 0.59, p = 0.68, high D levels (≥30ng/mL) 2 of 9 (22.2%), low D levels (<30ng/mL) 9 of 24 (37.5%), NNT 6.5.
	risk of severe case, 59.0% lower, RR 0.41, p = 0.13, high D levels (≥30ng/mL) 2 of 9 (22.2%), low D levels (<30ng/mL) 13 of 24 (54.2%), NNT 3.1.
[Baktash], 8/27/2020, prospective, United Kingdom, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 28.6% lower, RR 0.71, p = 0.50, high D levels 4 of 31 (12.9%), low D levels 6 of 39 (15.4%), NNT 40, adjusted per study, >30nmol/L.
[Barassi], 1/25/2021, retrospective, Italy, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 64.9% lower, RR 0.35, p = 0.44, high D levels 1 of 31 (3.2%), low D levels 8 of 87 (9.2%), NNT 17, >20ng/mL.
	risk of mechanical ventilation, 64.9% lower, RR 0.35, p = 0.15, high D levels 2 of 31 (6.5%), low D levels 16 of 87 (18.4%), NNT 8.4, >20ng/mL.
[Basaran], 2/12/2021, retrospective, Turkey, Europe, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of severe case, 68.6% lower, RR 0.31, p = 0.005, high D levels 82 of 119 (68.9%), low D levels 80 of 85 (94.1%), NNT 4.0, odds ratio converted to relative risk, >10μg/L, per standard deviation increase in levels.
[Bayramoğlu], 3/31/2021, retrospective, Turkey, Europe, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of moderate/severe case, 69.5% lower, RR 0.30, p = 0.03, high D levels 10 of 60 (16.7%), low D levels 24 of 43 (55.8%), NNT 2.6, adjusted per study, odds ratio converted to relative risk, >12 ng/mL, multivariate logistic regression.
[Bennouar], 1/12/2021, prospective, Algeria, Africa, peer-reviewed, 4 authors. Submit Corrections or Updates.	risk of death, 85.5% lower, RR 0.14, p = 0.002, high D levels 4 of 30 (13.3%), low D levels 15 of 32 (46.9%), NNT 3.0, adjusted per study, >30μg/l vs. <10μg/l, proportional Cox regression.
	risk of death, 63.0% lower, RR 0.37, p = 0.10, high D levels 4 of 30 (13.3%), low D levels 14 of 35 (40.0%), NNT 3.7, adjusted per study, >30μg/l vs. 10-19μg/l, proportional Cox regression.
	risk of death, 23.1% lower, RR 0.77, p = 0.73, high D levels 4 of 30 (13.3%), low D levels 4 of 23 (17.4%), NNT 25, adjusted per study, >30μg/l vs. 20-29μg/l, proportional Cox regression.
[Bianconi], 7/1/2021, prospective, Italy, Europe, peer-reviewed, 12 authors. Submit Corrections or Updates.	risk of death, 17.5% lower, RR 0.82, p = 0.58, high D levels (≥12ng/ml) 94, low D levels (<12ng/ml) 106, model 3, Table S2, Cox proportional hazards.
	risk of death, 13.9% lower, RR 0.86, p = 0.73, high D levels (≥20ng/ml) 40, low D levels (<20ng/ml) 160, model 3, Table S2, Cox proportional hazards.
	risk of death/ICU, 15.9% lower, RR 0.84, p = 0.53, high D levels (≥12ng/ml) 94, low D levels (<12ng/ml) 106, model 3, Cox proportional hazards.
	risk of death/ICU, 10.9% lower, RR 0.89, p = 0.73, high D levels (≥20ng/ml) 40, low D levels (<20ng/ml) 160, model 3, Cox proportional hazards.
[Campi], 6/14/2021, prospective, Italy, Europe, peer-reviewed, 21 authors, dosage not specified, excluded in exclusion analyses: significant unadjusted differences between groups. Submit Corrections or Updates.	risk of death for severe patients, 24.3% lower, RR 0.76, p = 0.53, high D levels (≥20ng/ml) 6 of 39 (15.4%), low D levels (<20ng/ml) 13 of 64 (20.3%), NNT 20, hospitalized patients.
	risk of ICU for severe patients, 53.1% lower, RR 0.47, p < 0.001, high D levels (≥20ng/ml) 12 of 39 (30.8%), low D levels (<20ng/ml) 42 of 64 (65.6%), NNT 2.9, hospitalized patients.
[Carpagnano], 8/9/2020, retrospective, Italy, Europe, peer-reviewed, 10 authors. Submit Corrections or Updates.	risk of death at day 26, 70.6% lower, RR 0.29, p = 0.05, high D levels 5 of 34 (14.7%), low D levels 4 of 8 (50.0%), NNT 2.8, >30 ng/mL.
	risk of death at day 10, 90.0% lower, RR 0.10, p = 0.02, high D levels 2 of 34 (5.9%), low D levels 4 of 8 (50.0%), NNT 2.3, adjusted per study, >30 ng/mL.
[Cereda], 11/1/2020, prospective, Italy, Europe, peer-reviewed, 13 authors. Submit Corrections or Updates.	risk of death, 120.0% higher, RR 2.20, p = 0.04, high D levels 10 of 30 (33.3%), low D levels 24 of 99 (24.2%), odds ratio converted to relative risk, >20ng/mL.
	risk of ICU admission, 86.7% lower, RR 0.13, p = 0.59, high D levels 0 of 30 (0.0%), low D levels 5 of 99 (5.1%), NNT 20, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
[Charoenngam], 3/8/2021, retrospective, USA, North America, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of death, 34.1% lower, RR 0.66, p = 0.26, high D levels 12 of 100 (12.0%), low D levels 29 of 187 (15.5%), NNT 29, adjusted per study, odds ratio converted to relative risk, >=30ng/mL.
	risk of mechanical ventilation, 37.2% lower, RR 0.63, p = 0.17, high D levels 14 of 100 (14.0%), low D levels 34 of 187 (18.2%), NNT 24, adjusted per study, odds ratio converted to relative risk, >=30ng/mL.
	risk of ICU admission, 23.1% lower, RR 0.77, p = 0.28, high D levels 25 of 100 (25.0%), low D levels 56 of 187 (29.9%), NNT 20, adjusted per study, odds ratio converted to relative risk, >=30ng/mL.
	risk of death, 58.1% lower, RR 0.42, p = 0.05, high D levels 7 of 57 (12.3%), low D levels 25 of 79 (31.6%), NNT 5.2, adjusted per study, odds ratio converted to relative risk, >65 years old, >=30ng/mL.
[Cozier], 7/27/2021, prospective, USA, North America, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of case, 38.6% lower, RR 0.61, p = 0.04, high D levels 94 of 1,601 (5.9%), low D levels 33 of 373 (8.8%), NNT 34, adjusted per study, odds ratio converted to relative risk, >20ng/mL, multivariable.
[De Smet], 11/25/2020, retrospective, Belgium, Europe, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of death, 70.1% lower, RR 0.30, p = 0.02, high D levels 7 of 77 (9.1%), low D levels 20 of 109 (18.3%), NNT 11, adjusted per study, odds ratio converted to relative risk, >20ng/mL.
[Demir], 1/29/2021, retrospective, Turkey, Europe, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of severe case, 89.3% lower, RR 0.11, p < 0.001, high D levels 13, low D levels 99, ratio of the mean number of affected lung segments, >30ng/ml vs. <=10ng/mL.
	hospitalization time, 87.1% lower, relative time 0.13, p < 0.001, high D levels 13, low D levels 99, >30ng/ml vs. <=10ng/mL.
	risk of case, 24.2% lower, RR 0.76, p = 0.18, high D levels 13 of 31 (41.9%), low D levels 99 of 179 (55.3%), NNT 7.5, >30ng/ml vs. <=10ng/mL.
[Derakhshanian], 9/19/2021, retrospective, Iran, Middle East, peer-reviewed, 11 authors. Submit Corrections or Updates.	risk of death, 44.8% lower, RR 0.55, p = 0.05, high D levels 148, low D levels 142, odds ratio converted to relative risk, control prevalance approximated with overall prevalence.
	risk of mechanical ventilation, 41.7% lower, RR 0.58, p = 0.09, high D levels 148, low D levels 142, odds ratio converted to relative risk, control prevalance approximated with overall prevalence.
	risk of ICU admission, 37.3% lower, RR 0.63, p = 0.04, high D levels 148, low D levels 142, odds ratio converted to relative risk, control prevalance approximated with overall prevalence.
[di Filippo], 8/12/2021, retrospective, Italy, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 10.7% lower, RR 0.89, p = 1.00, high D levels 5 of 28 (17.9%), low D levels 12 of 60 (20.0%), NNT 47, >20ng/mL.
	risk of ICU admission, 41.6% lower, RR 0.58, p = 0.22, high D levels 6 of 28 (21.4%), low D levels 22 of 60 (36.7%), NNT 6.6, >20ng/mL.
	risk of severe case, 39.6% lower, RR 0.60, p = 0.04, high D levels 11 of 28 (39.3%), low D levels 39 of 60 (65.0%), NNT 3.9, >20ng/mL.
[Diaz-Curiel], 6/6/2021, retrospective, Spain, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of ICU admission, 73.2% lower, RR 0.27, p = 0.02, high D levels 3 of 214 (1.4%), low D levels 91 of 1,017 (8.9%), NNT 13, odds ratio converted to relative risk, >30ng/mL vs. <20ng/mL.
[Dror], 6/7/2021, retrospective, Israel, Middle East, preprint, 18 authors. Submit Corrections or Updates.	risk of severe or critical case, 85.1% lower, RR 0.15, p = 0.001, high D levels 109 of 120 (90.8%), low D levels 76 of 133 (57.1%), odds ratio converted to relative risk, >40ng/mL vs. <20ng/mL, multivariate logistic regression.
[Eden], 8/5/2021, retrospective, United Kingdom, Europe, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of death, 63.9% lower, RR 0.36, p = 0.10, high D levels (≥25nmol/L) 3 of 26 (11.5%), low D levels (<25nmol/L) 8 of 25 (32.0%), NNT 4.9.
	risk of death, 92.9% lower, RR 0.07, p = 0.18, high D levels (≥50nmol/L) 0 of 8 (0.0%), low D levels (<50nmol/L) 11 of 43 (25.6%), NNT 3.9, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
[Faniyi], 10/6/2020, prospective, United Kingdom, Europe, preprint, 10 authors. Submit Corrections or Updates.	risk of seropositive, 28.8% lower, RR 0.71, p = 0.003, high D levels 170 of 331 (51.4%), low D levels 44 of 61 (72.1%), NNT 4.8, >30nmol/L.
[Fatemi], 11/30/2021, prospective, Iran, Middle East, peer-reviewed, 5 authors, 1 October, 2020 - 31 May, 2021. Submit Corrections or Updates.	risk of death, 42.0% lower, RR 0.58, p = 0.07, high D levels 18 of 139 (12.9%), low D levels 25 of 109 (22.9%), NNT 10, odds ratio converted to relative risk, vitamin D measured prior to COVID-19, multivariate.
	risk of death, 51.1% lower, RR 0.49, p = 0.02, high D levels 13 of 115 (11.3%), low D levels 30 of 133 (22.6%), NNT 8.9, odds ratio converted to relative risk, vitamin D measured on admission, multivariate.
	risk of severe case, 37.9% lower, RR 0.62, p = 0.007, high D levels 38 of 139 (27.3%), low D levels 48 of 109 (44.0%), NNT 6.0, vitamin D measured prior to COVID-19.
	risk of severe case, 34.8% lower, RR 0.65, p = 0.02, high D levels 31 of 115 (27.0%), low D levels 55 of 133 (41.4%), NNT 6.9, vitamin D measured on admission.
[Faul], 6/30/2020, retrospective, Ireland, Europe, peer-reviewed, 9 authors. Submit Corrections or Updates.	risk of mechanical ventilation, 69.0% lower, RR 0.31, p = 0.03, high D levels 4 of 21 (19.0%), low D levels 8 of 12 (66.7%), NNT 2.1, adjusted per study, >30nmol/L.
[Freitas], 3/27/2021, retrospective, Portugal, Europe, preprint, 36 authors. Submit Corrections or Updates.	risk of death, 41.2% lower, RR 0.59, p = 0.02, high D levels 23 of 179 (12.8%), low D levels 68 of 311 (21.9%), NNT 11, >20ng/mL.
[Galaznik], 5/28/2021, retrospective, USA, North America, preprint, 6 authors. Submit Corrections or Updates.	risk of case, 35.1% lower, RR 0.65, p = 0.01, high D levels 13,903, low D levels 2,384, adjusted per study, breast cancer patients, logistic regression, RR approximated with OR.
	risk of case, 32.4% lower, RR 0.68, p = 0.05, high D levels 13,601, low D levels 1,318, adjusted per study, prostate cancer patients, logistic regression, RR approximated with OR.
[Gaudio], 3/27/2021, retrospective, Italy, Europe, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of case, 79.3% lower, RR 0.21, p < 0.001, high D levels 27 of 50 (54.0%) cases, 85 of 100 (85.0%) controls, NNT 2.7, case control OR.
[Gavioli], 2/19/2021, retrospective, USA, North America, peer-reviewed, 4 authors. Submit Corrections or Updates.	risk of death, 4.7% higher, RR 1.05, p = 0.83, high D levels 80 of 260 (30.8%), low D levels 52 of 177 (29.4%), >20ng/ml.
	risk of death, 44.8% lower, RR 0.55, p < 0.001, high D levels 102 of 376 (27.1%), low D levels 30 of 61 (49.2%), NNT 4.5, >10ng/ml.
	risk of oxygen therapy, 55.2% lower, RR 0.45, p < 0.001, high D levels 127 of 260 (48.8%), low D levels 116 of 177 (65.5%), NNT 6.0, adjusted per study, >20ng/ml, multivariate.
	risk of hospitalization, 3.6% lower, RR 0.96, p = 0.41, high D levels 218 of 260 (83.8%), low D levels 154 of 177 (87.0%), NNT 32, >20ng/ml.
[Golabi], 8/26/2021, retrospective, Iran, Middle East, peer-reviewed, 10 authors. Submit Corrections or Updates.	odds of symptoms, 90.0% lower, RR 0.10, p < 0.001, high D levels 34, low D levels 10, >30ng/mL vs. <20ng/mL, GEE regression, RR approximated with OR.
	odds of symptoms, 81.0% lower, RR 0.19, p = 0.006, high D levels 34, low D levels 9, 20-30ng/mL vs. <20ng/mL, GEE regression, RR approximated with OR.
	risk of case, 71.7% lower, RR 0.28, p = 0.07, high D levels 34 of 44 (77.3%) cases, 36 of 39 (92.3%) controls, NNT 3.5, case control OR, >30ng/mL vs. <20ng/mL.
[Gönen], 11/12/2021, retrospective, Turkey, Europe, peer-reviewed, 20 authors, dosage varies. Submit Corrections or Updates.	risk of death, 65.8% lower, RR 0.34, p = 0.62, high D levels (≥12ng/mL) 1 of 80 (1.2%), low D levels (<12ng/mL) 3 of 82 (3.7%), NNT 42, retrospective study.
	risk of ICU admission, 16.9% lower, RR 0.83, p = 1.00, high D levels (≥12ng/mL) 4 of 77 (5.2%), low D levels (<12ng/mL) 5 of 80 (6.2%), NNT 95, retrospective study.
	hospital stay >8 days, 21.1% lower, RR 0.79, p = 0.11, high D levels (≥12ng/mL) 40 of 78 (51.3%), low D levels (<12ng/mL) 52 of 80 (65.0%), NNT 7.3, retrospective study.
[Hastie], 8/26/2020, retrospective, population-based cohort, database analysis, United Kingdom, Europe, peer-reviewed, 14 authors. Submit Corrections or Updates.	risk of death, 17.4% lower, RR 0.83, p = 0.31, adjusted per study, multivariable Cox.
	risk of hospitalization, 9.1% lower, RR 0.91, p = 0.40, adjusted per study, multivariable Cox.
[Hernández], 10/27/2020, retrospective, Spain, Europe, peer-reviewed, 12 authors. Submit Corrections or Updates.	risk of combined death/ICU/ventilation, 83.0% lower, RR 0.17, p < 0.001, high D levels 35, low D levels 162, >= 20ng/mL risk of hospitalization * risk of death/ICU/ventilation \| hospitalization.
	risk of combined death/ICU/ventilation if hospitalized, 12.0% lower, RR 0.88, p = 0.86, high D levels 35, low D levels 162, >= 20ng/mL risk of death/ICU/ventilation \| hospitalization.
	risk of hospitalization, 80.6% lower, RR 0.19, p < 0.001, >= 20ng/mL.
[Hurst], 10/22/2021, prospective, United Kingdom, Europe, peer-reviewed, 23 authors. Submit Corrections or Updates.	risk of death, 68.4% lower, RR 0.32, p = 0.005, high D levels 68, low D levels 191, odds ratio converted to relative risk, >50nmol/l, multivariable, Supplementary Table 2, control prevalance approximated with overall prevalence.
	risk of mechanical ventilation, 66.0% lower, RR 0.34, p = 0.004, high D levels 6 of 68 (8.8%), low D levels 61 of 191 (31.9%), NNT 4.3, odds ratio converted to relative risk, >50nmol/l, multivariable, Supplementary Table 2.
[Im], 8/11/2020, retrospective, South Korea, Asia, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of case, 73.1% lower, RR 0.27, p < 0.001, high D levels 13 of 50 (26.0%) cases, 85 of 150 (56.7%) controls, NNT 4.3, case control OR.
[Infante], 2/18/2021, retrospective, Italy, Europe, peer-reviewed, 11 authors. Submit Corrections or Updates.	risk of death, 54.8% lower, RR 0.45, p = 0.05, high D levels 4 of 19 (21.1%), low D levels 55 of 118 (46.6%), NNT 3.9, >20ng/mL.
[Israel], 9/10/2020, retrospective, population-based cohort, Israel, Middle East, preprint, 8 authors. Submit Corrections or Updates.	risk of case, 21.3% lower, RR 0.79, p < 0.001, high D levels 2,601 of 32,712 (8.0%), low D levels 5,011 of 39,485 (12.7%), NNT 21, adjusted per study, odds ratio converted to relative risk, multivariable >75 nmol/L vs. <30 nmol/L.
[Jain], 11/19/2020, prospective, India, South Asia, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of death, 85.2% lower, RR 0.15, p = 0.001, high D levels 2 of 64 (3.1%), low D levels 19 of 90 (21.1%), NNT 5.6, >20ng/mL.
	risk of ICU admission, 95.4% lower, RR 0.05, p < 0.001, high D levels 2 of 64 (3.1%), low D levels 61 of 90 (67.8%), NNT 1.5, >20ng/mL.
[Jimenez], 7/26/2021, retrospective, Spain, Europe, peer-reviewed, 21 authors, 12 March, 2020 - 21 May, 2020, dosage paricalcitol 0.9μg weekly, excluded in exclusion analyses: many patients received vitamin D treatment. Submit Corrections or Updates.	risk of death, 7.7% higher, RR 1.08, p = 0.81, high D levels 50, low D levels 110, >30 vs. <20ng/ml, RR approximated with OR, excluded in exclusion analyses: many patients received vitamin D treatment.
	risk of mechanical ventilation, 47.5% lower, RR 0.53, p = 0.56, high D levels 50, low D levels 110, >30 vs. <20ng/ml, RR approximated with OR, excluded in exclusion analyses: many patients received vitamin D treatment.
	risk of ICU admission, 12.2% lower, RR 0.88, p = 0.87, high D levels 50, low D levels 110, >30 vs. <20ng/ml, RR approximated with OR, excluded in exclusion analyses: many patients received vitamin D treatment.
	risk of hospitalization, 0.8% lower, RR 0.99, p = 0.98, high D levels 50, low D levels 110, >30 vs. <20ng/ml, RR approximated with OR, excluded in exclusion analyses: many patients received vitamin D treatment.
[Jude], 6/17/2021, retrospective, United Kingdom, Europe, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of hospitalization, 71.6% lower, RR 0.28, p < 0.001, adjusted per study, odds ratio converted to relative risk, >25 nmol/L, control prevalence approximated with overall prevalence.
	risk of hospitalization, 57.9% lower, RR 0.42, p < 0.001, adjusted per study, odds ratio converted to relative risk, >50 nmol/L, control prevalence approximated with overall prevalence.
[Karahan], 10/5/2020, retrospective, Turkey, Europe, peer-reviewed, 2 authors. Submit Corrections or Updates.	risk of death, 82.5% lower, RR 0.17, p < 0.001, high D levels 5 of 46 (10.9%), low D levels 64 of 103 (62.1%), NNT 2.0, >20nmol/L.
[Karonova], 8/29/2021, retrospective, Russia, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 77.8% lower, RR 0.22, p = 0.006, high D levels 8 of 96 (8.3%), low D levels 10 of 37 (27.0%), NNT 5.3, adjusted per study, odds ratio converted to relative risk, >10ng/mL, logistic regression model 2.
	risk of death, 84.8% lower, RR 0.15, p = 0.06, high D levels 1 of 43 (2.3%), low D levels 17 of 90 (18.9%), NNT 6.0, adjusted per study, odds ratio converted to relative risk, >20ng/mL, logistic regression model 2.
	risk of severe case, 67.3% lower, RR 0.33, p = 0.005, high D levels 12 of 96 (12.5%), low D levels 13 of 37 (35.1%), NNT 4.4, adjusted per study, odds ratio converted to relative risk, >10ng/mL, logistic regression model 2.
	risk of severe case, 53.2% lower, RR 0.47, p = 0.13, high D levels 4 of 43 (9.3%), low D levels 21 of 90 (23.3%), NNT 7.1, adjusted per study, odds ratio converted to relative risk, >20ng/mL, logistic regression model 2.
[Karonova (B)], 12/31/2020, retrospective, Russia, Europe, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of death, 79.4% lower, RR 0.21, p = 0.11, high D levels 1 of 23 (4.3%), low D levels 12 of 57 (21.1%), NNT 6.0, odds ratio converted to relative risk, >20ng/ml.
	risk of severe case, 71.1% lower, RR 0.29, p = 0.07, high D levels 3 of 23 (13.0%), low D levels 22 of 57 (38.6%), NNT 3.9, odds ratio converted to relative risk, >20ng/ml.
[Katz], 12/4/2020, retrospective, population-based cohort, USA, North America, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of case, 78.4% lower, RR 0.22, p < 0.001, high D levels 85 of 101,175 (0.1%), low D levels 87 of 31,950 (0.3%), NNT 531, adjusted per study.
[Kaufman], 9/17/2020, retrospective, population-based cohort, USA, North America, peer-reviewed, median age 54.0, 5 authors. Submit Corrections or Updates.	risk of case, 53.0% lower, RR 0.47, p < 0.001, high D levels 12,321, low D levels 39,190, >55 ng/mL vs. <20 ng/mL.
[Kaur], 11/30/2021, prospective, India, South Asia, peer-reviewed, 5 authors, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 89.8% lower, RR 0.10, p < 0.001, high D levels (≥10ng/mL) 5 of 64 (7.8%), low D levels (<10ng/mL) 13 of 17 (76.5%), NNT 1.5.
	risk of mechanical ventilation, 90.3% lower, RR 0.10, p < 0.001, high D levels (≥10ng/mL) 4 of 64 (6.2%), low D levels (<10ng/mL) 11 of 17 (64.7%), NNT 1.7.
[Lau], 4/28/2020, retrospective, USA, North America, preprint, 7 authors. Submit Corrections or Updates.	risk of ICU admission, 45.0% lower, RR 0.55, p = 0.29, high D levels 2 of 5 (40.0%), low D levels 11 of 15 (73.3%), NNT 3.0, >30ng/mL.
[Li], 5/19/2021, retrospective, USA, North America, peer-reviewed, 4 authors. Submit Corrections or Updates.	risk of case, 8.6% lower, RR 0.91, p = 0.24, high D levels 610 of 13,650 (4.5%), low D levels 290 of 4,498 (6.4%), NNT 51, adjusted per study, odds ratio converted to relative risk, >20ng/mL, Figure 2.
	risk of case, 12.4% lower, RR 0.88, p = 0.07, high D levels 289 of 7,272 (4.0%), low D levels 611 of 10,876 (5.6%), NNT 61, adjusted per study, odds ratio converted to relative risk, >30ng/mL, Figure 2.
[Li (B)], 1/11/2021, retrospective, population-based cohort, United Kingdom, Europe, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of severe case, 36.2% lower, RR 0.64, p < 0.001, NNT 932, odds ratio converted to relative risk, >25nmol/L.
	risk of hospitalization, 28.8% lower, RR 0.71, p < 0.001, NNT 261, odds ratio converted to relative risk, >25nmol/L.
	risk of case, 29.5% lower, RR 0.71, p < 0.001, NNT 823, odds ratio converted to relative risk, >25nmol/L.
[Livingston], 4/2/2021, retrospective, United Kingdom, Europe, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of case, 50.9% lower, RR 0.49, p = 0.02, high D levels 16 of 52 (30.8%), low D levels 31 of 52 (59.6%), NNT 3.5, odds ratio converted to relative risk, >34.4nmol/L.
[Lohia], 3/4/2021, retrospective, USA, North America, peer-reviewed, 4 authors. Submit Corrections or Updates.	risk of death, 14.7% lower, RR 0.85, p = 0.56, high D levels 88, low D levels 95, odds ratio converted to relative risk, control prevalence approximated with overall prevalence, >30 ng/mL vs. <20 ng/mL, >30 ng/mL group size approximated.
	risk of mechanical ventilation, 18.9% lower, RR 0.81, p = 0.48, high D levels 88, low D levels 95, odds ratio converted to relative risk, control prevalence approximated with overall prevalence, >30 ng/mL vs. <20 ng/mL, >30 ng/mL group size approximated.
	risk of ICU admission, 28.5% lower, RR 0.72, p = 0.17, high D levels 88, low D levels 95, odds ratio converted to relative risk, control prevalence approximated with overall prevalence, >30 ng/mL vs. <20 ng/mL, >30 ng/mL group size approximated.
[Luo], 11/13/2020, retrospective, China, Asia, peer-reviewed, median age 56.0, 5 authors. Submit Corrections or Updates.	risk of progression, 63.0% lower, RR 0.37, p = 0.01, high D levels 335, low D levels 560, >30nmol/L.
[Ma], 12/3/2021, retrospective, USA, North America, peer-reviewed, 16 authors, May 2020 - March 2021, dosage varies. Submit Corrections or Updates.	risk of hospitalization, 67.0% lower, RR 0.33, p = 0.15, high D levels 7,893, low D levels 7,823, adjusted per study, highest quintile vs. lowest quintile predicted vitamin D levels, model 3, supplemental table 3, multivariable, RR approximated with OR.
	risk of symptomatic case, 9.0% lower, RR 0.91, p = 0.52, high D levels 7,893, low D levels 7,823, adjusted per study, highest quintile vs. lowest quintile predicted vitamin D levels, model 3, supplemental table 3, multivariable, RR approximated with OR.
	risk of case, 52.0% lower, RR 0.48, p = 0.01, high D levels 7,893, low D levels 7,823, adjusted per study, highest quintile vs. lowest quintile predicted vitamin D levels, model 3, supplemental table 3, multivariable, RR approximated with OR.
[Macaya], 10/21/2020, retrospective, Spain, Europe, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of severe case, 55.0% lower, RR 0.45, p = 0.07, high D levels 11 of 35 (31.4%), low D levels 20 of 45 (44.4%), NNT 7.7, odds ratio converted to relative risk, >20ng/mL.
[Maghbooli], 9/25/2020, retrospective, Iran, Middle East, peer-reviewed, 11 authors. Submit Corrections or Updates.	risk of death, 51.7% lower, RR 0.48, p = 0.08, high D levels 7 of 72 (9.7%), low D levels 27 of 134 (20.1%), NNT 9.6, age >40.
	risk of mechanical ventilation, 31.6% lower, RR 0.68, p = 0.49, high D levels 6 of 77 (7.8%), low D levels 18 of 158 (11.4%), NNT 28.
	risk of ICU admission, 32.0% lower, RR 0.68, p = 0.33, high D levels 11 of 77 (14.3%), low D levels 33 of 158 (20.9%), NNT 15, >30nmol/L.
[Matin], 7/30/2021, retrospective, case control, Iran, Middle East, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of case, 66.1% lower, RR 0.34, p < 0.001, case control OR, >20ng/mL.
[Mazziotti], 3/5/2021, retrospective, Italy, Europe, peer-reviewed, 11 authors, dosage varies. Submit Corrections or Updates.	risk of death, 2.4% lower, RR 0.98, p = 0.91, high D levels 187, low D levels 161, odds ratio converted to relative risk, >12ng/mL, control prevalance approximated with overall prevalence.
	risk of acute hypoxemic respiratory failure, 37.0% lower, RR 0.63, p = 0.006, high D levels 72 of 187 (38.5%), low D levels 97 of 161 (60.2%), NNT 4.6, odds ratio converted to relative risk, >12ng/mL.
[Meltzer], 3/19/2021, retrospective, database analysis, USA, North America, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of case, 34.6% lower, RR 0.65, p = 0.11, high D levels 61 of 1,097 (5.6%), low D levels 118 of 1,251 (9.4%), NNT 26, adjusted per study, >40ng/mL vs. <20ng/mL, Table 2, Model 2.
[Meltzer (B)], 9/3/2020, retrospective, USA, North America, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of case, 43.5% lower, RR 0.56, p = 0.02, high D levels 39 of 317 (12.3%), low D levels 32 of 172 (18.6%), NNT 16, adjusted per study, >20ng/mL.
[Mendy], 6/27/2020, retrospective, USA, North America, preprint, 4 authors. Submit Corrections or Updates.	risk of death, 7.0% lower, RR 0.93, p = 0.89, high D levels 21 of 600 (3.5%), low D levels 5 of 89 (5.6%), NNT 47, odds ratio converted to relative risk.
	risk of death/ICU, 16.7% lower, RR 0.83, p < 0.001, high D levels 68 of 600 (11.3%), low D levels 23 of 89 (25.8%), NNT 6.9, odds ratio converted to relative risk.
	risk of ICU admission, 55.3% lower, RR 0.45, p = 0.008, high D levels 47 of 600 (7.8%), low D levels 18 of 89 (20.2%), NNT 8.1, odds ratio converted to relative risk.
	risk of hospitalization, 15.1% lower, RR 0.85, p < 0.001, high D levels 171 of 600 (28.5%), low D levels 45 of 89 (50.6%), NNT 4.5, odds ratio converted to relative risk.
[Merzon], 7/23/2020, retrospective, Israel, Middle East, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of hospitalization, 46.4% lower, RR 0.54, p = 0.06, high D levels 79, low D levels 703, odds ratio converted to relative risk, >30ng/mL.
	risk of case, 28.4% lower, RR 0.72, p < 0.001, high D levels 1,139, low D levels 6,668, odds ratio converted to relative risk, >30ng/mL.
[Nimavat], 8/5/2021, retrospective, India, South Asia, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of death, 50.4% lower, RR 0.50, p = 0.17, high D levels 13 of 131 (9.9%), low D levels 5 of 25 (20.0%), NNT 9.9, >10ng/mL, within cases.
	risk of severe case, 67.6% lower, RR 0.32, p = 0.003, high D levels 17 of 131 (13.0%), low D levels 10 of 25 (40.0%), NNT 3.7, >10ng/mL, within cases.
[Orchard], 1/19/2021, retrospective, United Kingdom, Europe, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of ICU admission, 58.8% lower, RR 0.41, p = 0.001, high D levels 9 of 40 (22.5%), low D levels 41 of 75 (54.7%), NNT 3.1, all hospitalized patients, >50 nmol/L.
	risk of death, 24.1% lower, RR 0.76, p = 1.00, high D levels 1 of 9 (11.1%), low D levels 6 of 41 (14.6%), NNT 28, ICU patients only, >50 nmol/L.
	risk of mechanical ventilation, 8.9% lower, RR 0.91, p = 0.70, high D levels 6 of 9 (66.7%), low D levels 30 of 41 (73.2%), NNT 15, ICU patients only, >50 nmol/L.
[Panagiotou], 6/30/2020, retrospective, United Kingdom, Europe, preprint, 12 authors. Submit Corrections or Updates.	risk of ICU admission, 52.0% lower, RR 0.48, p = 0.02, high D levels 8 of 44 (18.2%), low D levels 34 of 90 (37.8%), NNT 5.1, >50nmol/L.
[Parra-Ortega], 8/24/2021, prospective, Mexico, North America, peer-reviewed, 9 authors, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 98.7% lower, RR 0.01, p < 0.001, high D levels (≥20ng/dL) 0 of 15 (0.0%), low D levels (<20ng/dL) 63 of 79 (79.7%), NNT 1.3, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), unadjusted.
[Pecina], 8/27/2021, retrospective, USA, North America, peer-reviewed, 4 authors, dosage not specified, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 35.9% lower, RR 0.64, p = 0.74, high D levels (≥20ng/mL) 6 of 77 (7.8%), low D levels (<20ng/mL) 1 of 15 (6.7%), odds ratio converted to relative risk, multivariable logistic regression.
	risk of mechanical ventilation, 56.9% lower, RR 0.43, p = 0.22, high D levels (≥20ng/mL) 8 of 15 (53.3%), low D levels (<20ng/mL) 4 of 15 (26.7%), odds ratio converted to relative risk, multivariable logistic regression.
	risk of ICU admission, 13.1% higher, RR 1.13, p = 0.57, high D levels (≥20ng/mL) 54 of 77 (70.1%), low D levels (<20ng/mL) 9 of 15 (60.0%), odds ratio converted to relative risk, multivariable logistic regression.
[Pepkowitz], 9/29/2020, retrospective, USA, North America, preprint, 7 authors. Submit Corrections or Updates.	risk of ICU admission, 55.8% lower, RR 0.44, p = 0.01, high D levels (≥20ng/mL) 9 of 24 (37.5%), low D levels (<20ng/mL) 11 of 13 (84.6%), NNT 2.1.
[Pimental], 5/31/2021, retrospective, Brazil, South America, peer-reviewed, 3 authors. Submit Corrections or Updates.	risk of death, 29.4% lower, RR 0.71, p = 1.00, high D levels 3 of 17 (17.6%), low D levels 2 of 8 (25.0%), NNT 14, >20ng/mL.
[Putra], 12/10/2021, retrospective, Indonesia, South Asia, peer-reviewed, 3 authors, February 2020 - September 2020. Submit Corrections or Updates.	risk of hospitalization, 25.6% lower, RR 0.74, p = 0.59, high D levels 9 of 31 (29.0%) cases, 11 of 31 (35.5%) controls, NNT 14, case control OR.
[Radujkovic], 9/10/2020, prospective, Germany, Europe, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of death, 93.2% lower, RR 0.07, p = 0.001, high D levels 144, low D levels 12, >30nmol/L.
	risk of death/intubation, 84.0% lower, RR 0.16, p < 0.001, high D levels 144, low D levels 12, >30nmol/L.
[Ramirez-Sandoval], 10/15/2021, retrospective, Mexico, North America, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of death, 31.5% lower, RR 0.68, p < 0.001, high D levels 2,337, low D levels 571, adjusted per study, >12.5ng/mL, 30 day in-hospital mortality.
	hospitalization time, 22.2% lower, relative time 0.78, p < 0.001, high D levels 2,337, low D levels 571.
[Ribeiro], 8/5/2021, retrospective, Brazil, South America, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of case, 50.5% lower, RR 0.50, p = 0.01, >30ng/mL, multivariate, RR approximated with OR.
[Ricci], 3/3/2021, retrospective, Italy, Europe, peer-reviewed, 15 authors. Submit Corrections or Updates.	risk of death, 87.6% lower, RR 0.12, p = 0.07, high D levels 0 of 30 (0.0%), low D levels 3 of 22 (13.6%), NNT 7.3, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >10 ng/mL.
[Savitri], 5/8/2021, retrospective, Indonesia, South Asia, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of symptomatic case, 88.0% lower, RR 0.12, p < 0.001, high D levels 3 of 25 (12.0%), low D levels 17 of 17 (100.0%), NNT 1.1, >20ng/ml.
[Seven], 11/23/2021, prospective, Turkey, Europe, peer-reviewed, 6 authors, September 2020 - November 2020. Submit Corrections or Updates.	risk of severe disease or poor prognostic factor, 46.5% lower, RR 0.53, p = 0.006.
[Sinaci], 8/11/2021, retrospective, Turkey, Europe, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of moderate/severe case, 79.5% lower, RR 0.21, p < 0.001, high D levels (≥10ng/mL) 8 of 100 (8.0%), low D levels (<10ng/mL) 23 of 59 (39.0%), NNT 3.2.
	risk of case, 59.9% lower, RR 0.40, p < 0.001, high D levels (≥10ng/mL) 100 of 397 (25.2%), low D levels (<10ng/mL) 59 of 94 (62.8%), NNT 2.7.
[Sulli], 2/24/2021, retrospective, Italy, Europe, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 79.2% lower, RR 0.21, p < 0.001, high D levels 28 of 65 (43.1%) cases, 51 of 65 (78.5%) controls, NNT 2.7, case control OR, >10ng/mL.
[Susianti], 2/12/2021, retrospective, Indonesia, South Asia, peer-reviewed, 8 authors. Submit Corrections or Updates.	risk of death, 91.5% lower, RR 0.09, p = 0.32, high D levels 0 of 8 (0.0%), low D levels 9 of 42 (21.4%), NNT 4.7, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >49.92 nmol/L.
	risk of ICU admission, 90.5% lower, RR 0.10, p = 0.32, high D levels 0 of 8 (0.0%), low D levels 8 of 42 (19.0%), NNT 5.2, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >49.92 nmol/L.
	risk of progression, 81.5% lower, RR 0.19, p = 0.04, high D levels 8, low D levels 42, ISTH DIC>=5, >49.92 nmol/L, bivariate, RR approximated with OR.
	risk of progression, 44.4% lower, RR 0.56, p = 0.03, high D levels 8, low D levels 42, increased D-dimer >2 mg/L, >49.92 nmol/L, multivariate, RR approximated with OR.
[Szeto], 12/30/2020, retrospective, USA, North America, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of death, 5.6% higher, RR 1.06, p = 1.00, high D levels 14 of 58 (24.1%), low D levels 8 of 35 (22.9%).
	risk of mechanical ventilation, 39.7% lower, RR 0.60, p = 0.21, high D levels 10 of 58 (17.2%), low D levels 10 of 35 (28.6%), NNT 8.8.
	risk of no hospital discharge, 26.7% higher, RR 1.27, p = 0.50, high D levels 21 of 58 (36.2%), low D levels 10 of 35 (28.6%).
[Sánchez-Zuno], 5/28/2021, prospective, Mexico, North America, peer-reviewed, 12 authors, dosage 10,000IU days 1-14. Submit Corrections or Updates.	risk of severe case, 5.6% lower, RR 0.94, p = 1.00, high D levels 4 of 8 (50.0%), low D levels 18 of 34 (52.9%), NNT 34, >30ng/mL, >4 symptoms.
[Tehrani], 1/25/2021, retrospective, Iran, Middle East, peer-reviewed, 5 authors. Submit Corrections or Updates.	risk of death, 47.5% lower, RR 0.52, p = 0.07, high D levels 34 of 180 (18.9%), low D levels 9 of 25 (36.0%), NNT 5.8, >10ng/ml.
[Tomasa-Irriguible], 10/26/2020, retrospective, Spain, Europe, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of mechanical ventilation, 35.0% lower, RR 0.65, p = 0.21, high D levels 15 of 27 (55.6%), low D levels 18 of 78 (23.1%), adjusted per study, odds ratio converted to relative risk, ≥20 ng/mL, bivariate logistic regression.
	risk of ICU admission, 16.9% lower, RR 0.83, p = 0.58, high D levels 0 of 27 (0.0%), low D levels 17 of 78 (21.8%), NNT 4.6, adjusted per study, odds ratio converted to relative risk, ≥20 ng/mL, bivariate logistic regression.
[Vanegas-Cedillo], 3/14/2021, retrospective, Mexico, North America, preprint, 15 authors. Submit Corrections or Updates.	risk of death, 52.6% lower, RR 0.47, p = 0.006, high D levels 95 of 494 (19.2%), low D levels 21 of 57 (36.8%), NNT 5.7, adjusted per study, >12ng/mL.
[Vasheghani], 1/18/2021, retrospective, Iran, Middle East, preprint, 6 authors, dosage not specified. Submit Corrections or Updates.	risk of ICU admission, 63.8% lower, RR 0.36, p = 0.009, high D levels 13 of 185 (7.0%), low D levels 53 of 323 (16.4%), NNT 11, adjusted per study, vitamin D levels >30ng/mL.
[Vassiliou], 12/9/2020, prospective, Greece, Europe, peer-reviewed, 6 authors. Submit Corrections or Updates.	risk of death, 90.9% lower, RR 0.09, p = 0.04, high D levels 0 of 15 (0.0%), low D levels 5 of 15 (33.3%), NNT 3.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >15.2ng/mL.
[Walk], 11/9/2020, retrospective, Netherlands, Europe, preprint, 5 authors. Submit Corrections or Updates.	risk of death/intubation, 0.4% higher, RR 1.00, p = 1.00, high D levels 48 of 110 (43.6%), low D levels 10 of 23 (43.5%), >25nmol/L.
[Ye], 10/13/2020, retrospective, China, Asia, peer-reviewed, 18 authors. Submit Corrections or Updates.	risk of severe/critical COVID-19, 93.4% lower, RR 0.07, p = 0.03, high D levels 2 of 36 (5.6%), low D levels 8 of 26 (30.8%), NNT 4.0, adjusted per study, >50nmol/L.
[Yılmaz], 10/5/2020, retrospective, Turkey, Europe, peer-reviewed, 2 authors. Submit Corrections or Updates.	risk of severe case, 73.4% lower, RR 0.27, p = 1.00, high D levels 0 of 11 (0.0%), low D levels 2 of 29 (6.9%), NNT 14, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >20ng/ml.
	risk of moderate or severe case, 41.4% lower, RR 0.59, p = 0.69, high D levels 2 of 11 (18.2%), low D levels 9 of 29 (31.0%), NNT 7.8, >20ng/ml.
[Zelzer], 6/22/2021, retrospective, Austria, Europe, peer-reviewed, 7 authors. Submit Corrections or Updates.	risk of death, 46.4% lower, RR 0.54, p = 0.08, high D levels 24 of 121 (19.8%), low D levels 10 of 27 (37.0%), NNT 5.8, >30nmol/L.
[Ünsal], 4/5/2021, retrospective, Turkey, Europe, peer-reviewed, 10 authors. Submit Corrections or Updates.	risk of death, 80.6% lower, RR 0.19, p = 0.23, high D levels 0 of 29 (0.0%), low D levels 2 of 27 (7.4%), NNT 14, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), >=20ng/mL.
	risk of oxygen therapy, 73.4% lower, RR 0.27, p = 0.07, high D levels 2 of 29 (6.9%), low D levels 7 of 27 (25.9%), NNT 5.3, >=20ng/mL.

Early treatment

[Annweiler], 11/2/2020, retrospective, France, Europe, peer-reviewed, 7 authors, dosage 80,000IU single dose. Submit Corrections or Updates.	risk of death, 63.0% lower, RR 0.37, p = 0.28, treatment 3 of 16 (18.8%), control 10 of 32 (31.2%), NNT 8.0, adjusted per study, supplementation after diagnosis.
[Annweiler (B)], 10/13/2020, retrospective, France, Europe, peer-reviewed, mean age 87.7, 6 authors, dosage 80,000IU single dose, 80,000IU either in the week following the suspicion or diagnosis of COVID-19, or during the previous month. Submit Corrections or Updates.	risk of death, 89.0% lower, RR 0.11, p = 0.002, treatment 10 of 57 (17.5%), control 5 of 9 (55.6%), NNT 2.6, adjusted per study.
[Asimi], 5/22/2021, retrospective, Bosnia and Herzegovina, Europe, preprint, 3 authors, dosage 2,000IU daily, this trial uses multiple treatments in the treatment arm (combined with zinc and selenium) - results of individual treatments may vary, excluded in exclusion analyses: excessive unadjusted differences between groups. Submit Corrections or Updates.	risk of mechanical ventilation, 97.4% lower, RR 0.03, p < 0.001, treatment 0 of 270 (0.0%), control 9 of 86 (10.5%), NNT 9.6, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), unadjusted.
	risk of hospitalization, 99.0% lower, RR 0.010, p < 0.001, treatment 0 of 270 (0.0%), control 24 of 86 (27.9%), NNT 3.6, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), unadjusted.
	risk of severe case, 99.5% lower, RR 0.005, p < 0.001, treatment 0 of 270 (0.0%), control 51 of 86 (59.3%), NNT 1.7, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), unadjusted.
[Burahee], 2/17/2021, retrospective, United Kingdom, Europe, peer-reviewed, 4 authors, dosage 100,000IU days 1-4, additional 200000IU over four weeks if serum level insufficient. Submit Corrections or Updates.	risk of death, 93.3% lower, RR 0.07, p = 0.01, treatment 0 of 12 (0.0%), control 2 of 2 (100.0%), NNT 1.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
[Efird], 12/31/2021, retrospective, USA, North America, peer-reviewed, 10 authors, 1 March, 2020 - 10 September, 2020, dosage varies. Submit Corrections or Updates.	risk of death, 48.9% lower, RR 0.51, p = 0.10, treatment 11 of 544 (2.0%), control 413 of 15,794 (2.6%), NNT 169, adjusted per study, non-hospitalized patients, vitamin D + no corticosteroids vs. no vitamin D + no corticosteroids.
	risk of death, 54.5% lower, RR 0.45, p = 0.02, treatment 11 of 192 (5.7%), control 553 of 4,340 (12.7%), NNT 14, adjusted per study, hospitalized patients, vitamin D + no corticosteroids vs. no vitamin D + no corticosteroids.
[Sánchez-Zuno (B)], 5/28/2021, Randomized Controlled Trial, Mexico, North America, peer-reviewed, 12 authors, dosage 10,000IU days 1-14. Submit Corrections or Updates.	risk of severe case, 89.4% lower, RR 0.11, p = 0.04, treatment 0 of 22 (0.0%), control 4 of 20 (20.0%), NNT 5.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), risk of >3 symptoms at day 14.
	risk of no recovery, 80.8% lower, RR 0.19, p = 0.22, treatment 0 of 22 (0.0%), control 2 of 20 (10.0%), NNT 10.0, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), risk of fever at day 14, Table S1.

Late treatment

[Alcala-Diaz], 5/21/2021, retrospective, Spain, Europe, peer-reviewed, 17 authors, dosage calcifediol 0.5mg day 1, 0.27mg day 3, 0.27mg day 7, 0.27mg day 14, 0.27mg day 21, 0.27mg day 28. Submit Corrections or Updates.	risk of death, 80.8% lower, RR 0.19, p = 0.04, treatment 4 of 79 (5.1%), control 90 of 458 (19.7%), NNT 6.9, adjusted per study, odds ratio converted to relative risk, day 30, multivariate logistic regression.
[Assiri], 8/28/2021, retrospective, Saudi Arabia, Middle East, peer-reviewed, 8 authors, dosage not specified, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 66.5% higher, RR 1.66, p = 0.60, treatment 12 of 90 (13.3%), control 2 of 28 (7.1%), odds ratio converted to relative risk.
[Beigmohammadi], 11/14/2021, Single Blind Randomized Controlled Trial, Iran, Middle East, peer-reviewed, 6 authors, dosage 600,000IU single dose, this trial uses multiple treatments in the treatment arm (combined with vitamins A, B, C, E) - results of individual treatments may vary. Submit Corrections or Updates.	risk of death, 88.9% lower, RR 0.11, p = 0.11, treatment 0 of 30 (0.0%), control 4 of 30 (13.3%), NNT 7.5, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
	risk of hospitalization >7 days, 41.0% lower, RR 0.59, p = 0.25, treatment 4 of 30 (13.3%), control 16 of 30 (53.3%), NNT 2.5, adjusted per study, odds ratio converted to relative risk.
	relative SOFA score @day 7, 45.5% better, RR 0.55, p < 0.001, treatment 30, control 30.
[Castillo], 8/29/2020, Randomized Controlled Trial, Spain, Europe, peer-reviewed, 7 authors, dosage calcifediol 0.5mg day 1, 0.27mg day 3, 0.27mg day 7, and then weekly until discharge or ICU admission. Submit Corrections or Updates.	risk of death, 85.4% lower, RR 0.15, p = 0.11, treatment 0 of 50 (0.0%), control 2 of 26 (7.7%), NNT 13, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
	risk of ICU admission, 94.2% lower, RR 0.06, p = 0.008, treatment 50, control 26, odds ratio converted to relative risk.
[Elamir], 9/8/2021, Randomized Controlled Trial, USA, North America, peer-reviewed, 9 authors, dosage calcitriol 0.5μg days 1-14. Submit Corrections or Updates.	risk of death, 85.7% lower, RR 0.14, p = 0.23, treatment 0 of 25 (0.0%), control 3 of 25 (12.0%), NNT 8.3, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
	risk of mechanical ventilation, 80.0% lower, RR 0.20, p = 0.48, treatment 0 of 25 (0.0%), control 2 of 25 (8.0%), NNT 12, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
	risk of ICU admission, 37.5% lower, RR 0.62, p = 0.33, treatment 5 of 25 (20.0%), control 8 of 25 (32.0%), NNT 8.3.
	hospitalization time, 40.5% lower, relative time 0.60, p = 0.14, treatment 25, control 25.
	relative Δ SaO₂/FiO₂, RR 0.14, p = 0.03, treatment 25, control 25.
[Giannini], 1/14/2021, retrospective, Italy, Europe, peer-reviewed, 21 authors, dosage 200,000IU days 1-2. Submit Corrections or Updates.	risk of death/ICU, 36.6% lower, RR 0.63, p = 0.13, treatment 14 of 36 (38.9%), control 29 of 55 (52.7%), NNT 7.2, odds ratio converted to relative risk.
[Güven], 7/23/2021, retrospective, Turkey, Europe, peer-reviewed, 2 authors, dosage 300,000IU single dose, excluded in exclusion analyses: very late stage, ICU patients. Submit Corrections or Updates.	risk of death, 24.8% lower, RR 0.75, p = 0.32, treatment 43 of 113 (38.1%), control 30 of 62 (48.4%), NNT 9.7, odds ratio converted to relative risk.
[Jevalikar], 12/28/2020, prospective, India, South Asia, peer-reviewed, 8 authors, dosage 60,000IU single dose, median total dose. Submit Corrections or Updates.	risk of death, 82.0% lower, RR 0.18, p = 0.12, treatment 1 of 128 (0.8%), control 3 of 69 (4.3%), NNT 28.
	risk of ICU admission, 33.7% lower, RR 0.66, p = 0.29, treatment 16 of 128 (12.5%), control 13 of 69 (18.8%), NNT 16.
	risk of oxygen therapy, 31.7% lower, RR 0.68, p = 0.06, treatment 38 of 128 (29.7%), control 30 of 69 (43.5%), NNT 7.3.
[Krishnan], 7/20/2020, retrospective, USA, North America, peer-reviewed, 13 authors, dosage not specified, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 19.0% lower, RR 0.81, p = 0.42, treatment 8 of 16 (50.0%), control 84 of 136 (61.8%), NNT 8.5.
[Lakkireddy], 2/23/2021, Randomized Controlled Trial, India, South Asia, peer-reviewed, mean age 45.5, 9 authors, dosage 60,000IU days 1-8, 8 or 10 days depending on BMI. Submit Corrections or Updates.	risk of death, 60.9% lower, RR 0.39, p = 0.27, treatment 2 of 44 (4.5%), control 5 of 43 (11.6%), NNT 14.
	risk of ICU admission, 21.8% lower, RR 0.78, p = 0.74, treatment 4 of 44 (9.1%), control 5 of 43 (11.6%), NNT 39.
	hospitalization time, 7.1% lower, relative time 0.93, p = 0.90, treatment 44, control 43.
[Leal], 10/25/2021, Randomized Controlled Trial, Mexico, North America, preprint, 7 authors, 1 September, 2020 - 28 February, 2021, dosage 2,000IU days 1-21, this trial uses multiple treatments in the treatment arm (combined with comprehensive nutritional support) - results of individual treatments may vary, excluded in exclusion analyses: combined treatments may contribute more to the effect seen. Submit Corrections or Updates.	risk of death, 85.7% lower, RR 0.14, p = 0.03, treatment 1 of 40 (2.5%), control 7 of 40 (17.5%), NNT 6.7.
	risk of mechanical ventilation, 57.1% lower, RR 0.43, p = 0.31, treatment 3 of 40 (7.5%), control 7 of 40 (17.5%), NNT 10.0.
[Ling], 12/11/2020, retrospective, United Kingdom, Europe, peer-reviewed, 7 authors, dosage 40,000IU weekly, regimen varied with 77% receiving a total of 40,000IU/week. Submit Corrections or Updates.	risk of death, 79.8% lower, RR 0.20, p < 0.001, treatment 73, control 253, odds ratio converted to relative risk, primary cohort.
	risk of death, 55.5% lower, RR 0.44, p = 0.02, treatment 80, control 443, odds ratio converted to relative risk, validation cohort.
[Lohia (B)], 3/4/2021, retrospective, USA, North America, peer-reviewed, 4 authors, dosage not specified. Submit Corrections or Updates.	risk of death, 10.7% lower, RR 0.89, p = 0.80, treatment 26, control 69, odds ratio converted to relative risk, <20 ng/mL, control prevalence approximated with overall prevalence.
	risk of mechanical ventilation, 26.9% lower, RR 0.73, p = 0.51, treatment 26, control 69, odds ratio converted to relative risk, <20 ng/mL, control prevalence approximated with overall prevalence.
	risk of ICU admission, 2.7% lower, RR 0.97, p = 0.93, treatment 26, control 69, odds ratio converted to relative risk, <20 ng/mL, control prevalence approximated with overall prevalence.
[Maghbooli (B)], 10/13/2021, Double Blind Randomized Controlled Trial, Iran, Middle East, peer-reviewed, 12 authors, dosage calcifediol 25μg daily, mean daily dose. Submit Corrections or Updates.	risk of death, 40.0% lower, RR 0.60, p = 0.72, treatment 3 of 53 (5.7%), control 5 of 53 (9.4%), NNT 26.
	risk of mechanical ventilation, 60.0% lower, RR 0.40, p = 0.44, treatment 2 of 53 (3.8%), control 5 of 53 (9.4%), NNT 18.
	risk of ICU admission, 40.0% lower, RR 0.60, p = 0.42, treatment 6 of 53 (11.3%), control 10 of 53 (18.9%), NNT 13.
	ICU time, 36.4% lower, relative time 0.64, p = 0.20, treatment 53, control 53.
	hospitalization time, 16.7% lower, relative time 0.83, p = 0.10, treatment 53, control 53.
[Mazziotti], 3/5/2021, retrospective, Italy, Europe, peer-reviewed, 11 authors, dosage varies. Submit Corrections or Updates.	risk of death, 19.0% lower, RR 0.81, p = 0.49, treatment 116, control 232, supplementation, RR approximated with OR.
	risk of mechanical ventilation, 67.0% higher, RR 1.67, p = 0.08, treatment 116, control 232, supplementation, RR approximated with OR.
[Murai], 11/17/2020, Double Blind Randomized Controlled Trial, Brazil, South America, peer-reviewed, 17 authors, dosage 200,000IU single dose, excluded in exclusion analyses: very late stage, >50% on oxygen/ventilation at baseline. Submit Corrections or Updates.	risk of death, 48.7% higher, RR 1.49, p = 0.43, treatment 9 of 119 (7.6%), control 6 of 118 (5.1%).
	risk of mechanical ventilation, 47.5% lower, RR 0.52, p = 0.09, treatment 9 of 119 (7.6%), control 17 of 118 (14.4%), NNT 15.
	risk of ICU admission, 24.6% lower, RR 0.75, p = 0.30, treatment 19 of 119 (16.0%), control 25 of 118 (21.2%), NNT 19.
[Nogués], 1/22/2021, prospective quasi-randomized (ward), Spain, Europe, peer-reviewed, 16 authors, dosage calcifediol 0.5mg day 1, 0.27mg day 3, 0.27mg day 7, 0.27mg day 15, 0.27mg day 30. Submit Corrections or Updates.	risk of death, 79.0% lower, RR 0.21, p = 0.001, treatment 21 of 447 (4.7%), control 62 of 391 (15.9%), NNT 9.0, adjusted per study, ITT.
	risk of death, 48.0% lower, RR 0.52, p = 0.001, treatment 500, control 338, adjusted per study, including patients treated later.
	risk of ICU admission, 87.0% lower, RR 0.13, p < 0.001, treatment 20 of 447 (4.5%), control 82 of 391 (21.0%), NNT 6.1, adjusted per study, ITT.
[Rastogi], 11/12/2020, Randomized Controlled Trial, India, South Asia, peer-reviewed, 8 authors, dosage 60,000IU days 1-7. Submit Corrections or Updates.	risk of no virological cure, 52.6% lower, RR 0.47, p = 0.02, treatment 6 of 16 (37.5%), control 19 of 24 (79.2%), NNT 2.4.
[Soliman], 9/1/2021, Randomized Controlled Trial, Egypt, Africa, peer-reviewed, 3 authors, dosage 200,000IU single dose. Submit Corrections or Updates.	risk of death, 63.4% lower, RR 0.37, p = 0.21, treatment 7 of 40 (17.5%), control 3 of 16 (18.8%), NNT 80, adjusted per study, odds ratio converted to relative risk, logistic regression.
	risk of mechanical ventilation, 20.0% lower, RR 0.80, p = 0.56, treatment 14 of 40 (35.0%), control 7 of 16 (43.8%), NNT 11, unadjusted.
	risk of no recovery, 20.0% lower, RR 0.80, p = 0.56, treatment 14 of 40 (35.0%), control 7 of 16 (43.8%), NNT 11, unadjusted.
[Tan], 6/10/2020, retrospective, Singapore, Asia, peer-reviewed, 14 authors, dosage 1,000IU daily. Submit Corrections or Updates.	risk of oxygen therapy, 80.5% lower, RR 0.20, p = 0.04, treatment 3 of 17 (17.6%), control 16 of 26 (61.5%), NNT 2.3, adjusted per study, multivariate.
	risk of ICU admission, 80.9% lower, RR 0.19, p = 0.07, treatment 1 of 17 (5.9%), control 8 of 26 (30.8%), NNT 4.0, no adjusted result available.
[Yildiz], 9/27/2021, retrospective, Turkey, Europe, peer-reviewed, 5 authors, dosage 300,000IU single dose. Submit Corrections or Updates.	risk of death, 80.9% lower, RR 0.19, p = 0.04, treatment 1 of 37 (2.7%), control 24 of 170 (14.1%), NNT 8.8.
	risk of ICU admission, 94.5% lower, RR 0.06, p = 0.13, treatment 0 of 37 (0.0%), control 14 of 170 (8.2%), NNT 12, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm).
	hospitalization time, 9.6% lower, relative time 0.90, p = 0.32, treatment 37, control 170.

Prophylaxis

[Abdulateef], 4/8/2021, retrospective, Iraq, Middle East, peer-reviewed, 7 authors, July 2020 - August 2020, dosage varies, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of hospitalization, 40.9% lower, RR 0.59, p = 0.30, treatment 6 of 127 (4.7%), control 24 of 300 (8.0%), NNT 31, unadjusted.
[Annweiler (C)], 11/2/2020, retrospective, France, Europe, peer-reviewed, 7 authors, dosage 50,000IU monthly, dose varies - 50,000 IU/month, or 80,000IU/100,000IU every 2–3 months. Submit Corrections or Updates.	risk of death, 93.0% lower, RR 0.07, p = 0.02, treatment 2 of 29 (6.9%), control 10 of 32 (31.2%), NNT 4.1, adjusted per study, regular bolus supplementation.
[Arroyo-Díaz], 9/24/2021, retrospective, Spain, Europe, peer-reviewed, 11 authors, dosage not specified. Submit Corrections or Updates.	risk of death, 12.4% higher, RR 1.12, p = 0.59, treatment 50 of 189 (26.5%), control 167 of 1,078 (15.5%), adjusted per study, odds ratio converted to relative risk.
	risk of mechanical ventilation, 43.3% lower, RR 0.57, p = 0.22, treatment 11 of 189 (5.8%), control 113 of 1,078 (10.5%), NNT 21, adjusted per study, odds ratio converted to relative risk.
	risk of ICU admission, 44.2% lower, RR 0.56, p = 0.03, treatment 13 of 189 (6.9%), control 133 of 1,078 (12.3%), NNT 18, unadjusted.
	hospitalization time, 11.8% lower, relative time 0.88, p = 0.20, treatment 189, control 1,078, unadjusted.
[Bagheri], 9/1/2021, retrospective, Iran, Middle East, peer-reviewed, 6 authors, dosage not specified. Submit Corrections or Updates.	risk of progression, 70.9% lower, RR 0.29, p = 0.02, treatment 131, control 379, adjusted per study, multinomial logistic regression, RR approximated with OR.
	risk of being in the hospitalized vs. outpatient group, 37.9% lower, RR 0.62, p = 0.11, treatment 28 of 131 (21.4%), control 143 of 379 (37.7%), NNT 6.1, adjusted per study, odds ratio converted to relative risk, binary logistic regression.
[Blanch-Rubió], 10/20/2020, retrospective, Spain, Europe, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 8.0% lower, RR 0.92, p = 0.68, treatment 62 of 1,303 (4.8%), control 47 of 799 (5.9%), NNT 89, adjusted per study.
[Campi], 6/14/2021, prospective, Italy, Europe, peer-reviewed, 21 authors, dosage not specified, excluded in exclusion analyses: significant unadjusted differences between groups. Submit Corrections or Updates.	risk of severe case, 88.4% lower, RR 0.12, p < 0.001, treatment 31 of 103 (30.1%) cases, 41 of 52 (78.8%) controls, NNT 2.3, case control OR, vitamin D supplementation, hospitalized patients vs. controls, excluded in exclusion analyses: significant unadjusted differences between groups.
[Cangiano], 12/22/2020, retrospective, Italy, Europe, peer-reviewed, 14 authors, dosage 25,000IU 2x per month. Submit Corrections or Updates.	risk of death, 70.0% lower, RR 0.30, p = 0.04, treatment 3 of 20 (15.0%), control 39 of 78 (50.0%), NNT 2.9.
[Cereda (B)], 11/11/2020, retrospective, Italy, Europe, peer-reviewed, 7 authors, dosage varies. Submit Corrections or Updates.	risk of death, 73.0% higher, RR 1.73, p = 0.14, treatment 7 of 18 (38.9%), control 40 of 152 (26.3%), odds ratio converted to relative risk, >=25,000IU/month for at least 3 months.
	risk of hospitalization, 17.3% higher, RR 1.17, p = 0.68, treatment 7 of 27 (25.9%), control 36 of 170 (21.2%), odds ratio converted to relative risk.
[Dudley], 5/18/2021, retrospective, United Kingdom, Europe, peer-reviewed, 5 authors, dosage 800IU daily. Submit Corrections or Updates.	risk of symptomatic case, 22.4% lower, RR 0.78, p = 0.65, treatment 15 of 58 (25.9%), control 2 of 6 (33.3%), NNT 13, positive test.
[Fasano], 6/2/2021, retrospective, Italy, Europe, peer-reviewed, 7 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 42.0% lower, RR 0.58, p = 0.05, treatment 13 of 329 (4.0%), control 92 of 1,157 (8.0%), NNT 25, odds ratio converted to relative risk.
[Golabi (B)], 8/26/2021, retrospective, Iran, Middle East, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 25.4% higher, RR 1.25, p = 0.56, treatment 28 of 53 (52.8%) cases, 25 of 53 (47.2%) controls, case control OR.
[Hernández (B)], 10/27/2020, retrospective, Spain, Europe, peer-reviewed, 12 authors, dosage varies. Submit Corrections or Updates.	risk of death, 3.7% higher, RR 1.04, p = 1.00, treatment 2 of 19 (10.5%), control 20 of 197 (10.2%).
	risk of mechanical ventilation, 75.9% lower, RR 0.24, p = 0.13, treatment 1 of 19 (5.3%), control 43 of 197 (21.8%), NNT 6.0.
	risk of ICU admission, 79.3% lower, RR 0.21, p = 0.05, treatment 1 of 19 (5.3%), control 50 of 197 (25.4%), NNT 5.0.
	hospitalization time, 33.3% lower, relative time 0.67, p = 0.11, treatment 19, control 197.
[Holt], 3/30/2021, prospective, United Kingdom, Europe, preprint, 31 authors, 1 May, 2020 - 5 February, 2021, dosage not specified, excluded in exclusion analyses: significant unadjusted confounding possible. Submit Corrections or Updates.	risk of case, 6.8% lower, RR 0.93, p = 0.53, treatment 141 of 5,640 (2.5%), control 305 of 9,587 (3.2%), NNT 147, adjusted per study, odds ratio converted to relative risk, fully adjusted, group sizes approximated.
[Israel (B)], 7/27/2021, retrospective, Israel, Middle East, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of hospitalization, 9.1% lower, RR 0.91, p = 0.003, treatment 737 of 2,406 (30.6%), control 6,216 of 18,453 (33.7%), NNT 33, odds ratio converted to relative risk, PCR+, cohort 2.
[Jimenez], 7/26/2021, retrospective, Spain, Europe, peer-reviewed, 21 authors, 12 March, 2020 - 21 May, 2020, dosage paricalcitol 0.9μg weekly. Submit Corrections or Updates.	risk of death, 50.1% lower, RR 0.50, p = 0.02, treatment 16 of 94 (17.0%), control 65 of 191 (34.0%), NNT 5.9, adjusted per study, paricalcitol treatment, multivariate Cox regression.
	risk of death, 50.7% lower, RR 0.49, p = 0.003, all vitamin D derivatives, univariate.
[Levitus], 5/3/2021, retrospective, USA, North America, peer-reviewed, 9 authors, dosage varies. Submit Corrections or Updates.	risk of severe case, 30.8% lower, RR 0.69, p = 0.25, treatment 65, control 64, odds ratio converted to relative risk, ≥1,000IU, control prevalence approximated with overall prevalence.
	risk of severe case, 40.0% lower, RR 0.60, p = 0.15, treatment 65, control 64, odds ratio converted to relative risk, ≥5,000IU, control prevalence approximated with overall prevalence.
	risk of severe case, no change, RR 1.00, p = 0.92, treatment 65, control 64, odds ratio converted to relative risk, ≥50,000IU, control prevalence approximated with overall prevalence.
[Louca], 11/30/2020, retrospective, population-based cohort, United Kingdom, Europe, peer-reviewed, 26 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 7.5% lower, RR 0.92, p < 0.001, odds ratio converted to relative risk, United Kingdom, all adjustment model.
[Loucera], 4/29/2021, retrospective, propensity score matching, Spain, Europe, peer-reviewed, 11 authors, dosage varies (calcifediol). Submit Corrections or Updates.	risk of death, 33.0% lower, RR 0.67, p = 0.009, treatment 374, control 374, calcifediol, <15 days before hospitalization, Cox model with inverse propensity weighting.
	risk of death, 27.0% lower, RR 0.73, p = 0.02, treatment 439, control 439, calcifediol, <30 days before hospitalization, Cox model with inverse propensity weighting.
	risk of death, 25.0% lower, RR 0.75, p = 0.005, treatment 570, control 570, cholecalciferol, <15 days before hospitalization, Cox model with inverse propensity weighting.
	risk of death, 12.0% lower, RR 0.88, p = 0.11, treatment 802, control 802, cholecalciferol, <30 days before hospitalization, Cox model with inverse propensity weighting.
[Lázaro], 9/5/2021, retrospective, Spain, Europe, preprint, 9 authors, dosage not specified, excluded in exclusion analyses: very few events, unadjusted results with no group details, minimal details provided. Submit Corrections or Updates.	risk of case, 26.8% lower, RR 0.73, p = 1.00, treatment 1 of 97 (1.0%), control 2 of 142 (1.4%), NNT 265.
[Ma], 12/3/2021, retrospective, USA, North America, peer-reviewed, 16 authors, May 2020 - March 2021, dosage varies. Submit Corrections or Updates.	risk of hospitalization, 49.0% lower, RR 0.51, p = 0.04, treatment 26,605, control 12,710, adjusted per study, supplementation ≥400 IU/day, model 3, supplemental table 3, multivariable, RR approximated with OR.
	risk of symptomatic case, 7.0% higher, RR 1.07, p = 0.25, treatment 7,895, control 31,420, adjusted per study, supplementation ≥2000 IU/day vs. <400 IU/day, model 3, supplemental table 3, multivariable, RR approximated with OR.
	risk of case, 17.0% lower, RR 0.83, p = 0.07, treatment 7,895, control 31,420, adjusted per study, supplementation ≥2000 IU/day vs. <400 IU/day, model 3, supplemental table 3, multivariable, RR approximated with OR.
[Ma (B)], 1/29/2021, retrospective, United Kingdom, Europe, peer-reviewed, 4 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 30.0% lower, RR 0.70, p = 0.03, treatment 49 of 363 (13.5%), control 1,329 of 7,934 (16.8%), NNT 31, adjusted per study, odds ratio converted to relative risk.
[Meltzer (C)], 3/19/2021, retrospective, database analysis, USA, North America, peer-reviewed, 6 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 36.0% lower, RR 0.64, p = 0.38, treatment 6 of 131 (4.6%), control 239 of 3,338 (7.2%), NNT 39, >=2,000IU/d.
	risk of case, 31.1% lower, RR 0.69, p = 0.16, treatment 15 of 304 (4.9%), control 239 of 3,338 (7.2%), NNT 45, >=1,001IU/d.
	risk of case, 8.9% lower, RR 0.91, p = 0.56, treatment 60 of 920 (6.5%), control 239 of 3,338 (7.2%), NNT 157, >=1IU/d.
[Mohseni], 8/4/2021, retrospective, Iran, Middle East, peer-reviewed, 4 authors, dosage not specified, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of case, 12.4% lower, RR 0.88, p = 0.09, treatment 99 of 192 (51.6%), control 242 of 411 (58.9%), NNT 14.
[Oristrell], 7/17/2021, retrospective, population-based cohort, Spain, Europe, peer-reviewed, 8 authors, dosage varies (calcifediol). Submit Corrections or Updates.	risk of death, 1.0% higher, RR 1.01, p = 0.91, calcifediol, univariate.
	risk of death, 4.0% lower, RR 0.96, p = 0.37, cholecalciferol, univariate.
	risk of case, 1.0% lower, RR 0.99, p = 0.65, NNT 3499, calcifediol, univariate.
	risk of case, 5.0% lower, RR 0.95, p = 0.004, cholecalciferol, multivariate.
[Oristrell (B)], 4/6/2021, retrospective, Spain, Europe, peer-reviewed, 10 authors, dosage calcitriol 0.3μg daily, mean daily dose. Submit Corrections or Updates.	risk of death, 43.0% lower, RR 0.57, p = 0.001, treatment 2,296, control 3,407, multivariate, patients with CKD stages 4-5.
	risk of severe case, 43.0% lower, RR 0.57, p < 0.001, treatment 2,296, control 3,407, multivariate, patients with CKD stages 4-5.
	risk of case, 22.0% lower, RR 0.78, p = 0.01, treatment 163 of 2,296 (7.1%), control 326 of 3,407 (9.6%), NNT 40, multivariate, patients with CKD stages 4-5.
[Pecina], 8/27/2021, retrospective, USA, North America, peer-reviewed, 4 authors, dosage not specified, excluded in exclusion analyses: unadjusted results with no group details. Submit Corrections or Updates.	risk of death, 70.0% higher, RR 1.70, p = 0.52, treatment 29, control 63, supplementation, unadjusted, RR approximated with OR, excluded in exclusion analyses: unadjusted results with no group details.
	risk of mechanical ventilation, 10.0% higher, RR 1.10, p = 0.89, treatment 29, control 63, supplementation, unadjusted, RR approximated with OR, excluded in exclusion analyses: unadjusted results with no group details.
	risk of ICU admission, 30.0% higher, RR 1.30, p = 0.61, treatment 29, control 63, supplementation, unadjusted, RR approximated with OR, excluded in exclusion analyses: unadjusted results with no group details.
[Sainz-Amo], 10/24/2020, retrospective, Spain, Europe, peer-reviewed, 13 authors. Submit Corrections or Updates.	risk of severe case, 32.7% lower, RR 0.67, p = 0.45, treatment 5 of 29 (17.2%) cases, 43 of 182 (23.6%) controls, NNT 23, case control OR.
	risk of case, 43.7% lower, RR 0.56, p = 0.23, treatment 6 of 39 (15.4%) cases, 42 of 172 (24.4%) controls, NNT 13, case control OR.
[Sinaci], 8/11/2021, retrospective, Turkey, Europe, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of severe case, 90.0% lower, RR 0.10, p = 0.35, treatment 0 of 36 (0.0%), control 7 of 123 (5.7%), NNT 18, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), supplementation.
	risk of moderate/severe case, 18.8% higher, RR 1.19, p = 0.64, treatment 8 of 36 (22.2%), control 23 of 123 (18.7%), supplementation.
[Sulli (B)], 2/24/2021, retrospective, Italy, Europe, peer-reviewed, 10 authors, dosage not specified. Submit Corrections or Updates.	risk of case, 75.6% lower, RR 0.24, p < 0.001, treatment 22 of 65 (33.8%) cases, 44 of 65 (67.7%) controls, NNT 3.0, case control OR, vitamin D supplementation.
[Vasheghani (B)], 1/18/2021, retrospective, Iran, Middle East, preprint, 6 authors, dosage not specified. Submit Corrections or Updates.	risk of death, 30.4% lower, RR 0.70, p = 0.45, treatment 7 of 88 (8.0%), control 48 of 420 (11.4%), NNT 29, vitamin D supplementation.
	risk of ICU admission, 63.8% lower, RR 0.36, p = 0.009, treatment 13 of 185 (7.0%), control 53 of 323 (16.4%), NNT 11, adjusted per study, vitamin D levels >30ng/mL.
[Ünsal (B)], 4/5/2021, retrospective, Turkey, Europe, peer-reviewed, 10 authors, dosage varies. Submit Corrections or Updates.	risk of pneumonia, 71.4% lower, RR 0.29, p = 0.009, treatment 4 of 28 (14.3%), control 14 of 28 (50.0%), NNT 2.8, average 800-1000IU/day cholecalciferol.

References

Abdollahi et al., Journal of Medical Virology, doi:10.1002/jmv.26726, The Association Between the Level of Serum 25(OH) Vitamin D, Obesity, and underlying Diseases with the risk of Developing COVID‐19 Infection: A case‐control study of hospitalized patients in Tehran, Iran, https://onlinelibrary.wiley.com/doi/abs/10.1002/jmv.26726.

Abdulateef et al., Open Medicine, doi:10.1515/med-2021-0273, COVID-19 severity in relation to sociodemographics and vitamin D use, https://www.degruyter.com/document/doi/10.1515/med-2021-0273/html.

Abrishami et al., European Journal of Nutrition, doi:10.1007/s00394-020-02411-0, Possible association of vitamin D status with lung involvement and outcome in patients with COVID-19: a retrospective study, https://link.springer.com/article/10.1007%2Fs00394-020-02411-0.

Afaghi et al., The Tohoku Journal of Experimental Medicine, doi:10.1620/tjem.255.127, Prevalence and Clinical Outcomes of Vitamin D Deficiency in COVID-19 Hospitalized Patients: A Retrospective Single-Center Analysis, https://www.jstage.jst.go.jp/artic..em/255/2/255_127/_article/-char/en.

Al-Daghri et al., Journal of Translational Medicine, doi:10.1186/s12967-021-02838-x, Vitamin D status of Arab Gulf residents screened for SARS-CoV-2 and its association with COVID-19 infection: a multi-centre case–control study, https://translational-medicine.bio..rticles/10.1186/s12967-021-02838-x.

Al-Salman et al., Nutrition & Food Science, doi:10.1108/NFS-05-2021-0143, In COVID-19 patients, low 25-hydroxyvitamin D level in serum is associated with longer viral clearance time and higher risk of intensive care unit admission, https://www.emerald.com/insight/co..10.1108/NFS-05-2021-0143/full/html.

Alcala-Diaz et al., Nutrients, doi:10.3390/nu13061760, Calcifediol Treatment and Hospital Mortality Due to COVID-19: A Cohort Study, https://www.mdpi.com/2072-6643/13/6/1760.

Alguwaihes et al., Cardiovascular Diabetology, doi:10.1186/s12933-020-01184-4, Diabetes and Covid-19 among hospitalized patients in Saudi Arabia: a single-centre retrospective study, https://link.springer.com/article/10.1186/s12933-020-01184-4.

Alpcan et al., Epidemiology & Infection, doi:10.1017/S0950268821001825, Vitamin D levels in children with COVID-19: a report from Turkey, https://www.cambridge.org/core/jou..y/627E5F7B744279CDBF0BD0CC12938C2C.

10.

AlSafar et al., Nutrients, doi:10.3390/nu13051714, COVID-19 Disease Severity and Death in Relation to Vitamin D Status among SARS-CoV-2-Positive UAE Residents, https://www.mdpi.com/2072-6643/13/5/1714/htm.

11.

Altman, D., BMJ, doi:10.1136/bmj.d2304, How to obtain the P value from a confidence interval, https://www.bmj.com/content/343/bmj.d2304.

12.

Altman (B) et al., BMJ, doi:10.1136/bmj.d2090, How to obtain the confidence interval from a P value, https://www.bmj.com/content/343/bmj.d2090.

13.

Amin et al., BMJ Nutrition, Prevention & Health, doi:10.1136/bmjnph-2020-000151, No evidence that vitamin D is able to prevent or affect the severity of COVID-19 in individuals with European ancestry: a Mendelian randomisation study of open data, https://nutrition.bmj.com/content/early/2021/01/07/bmjnph-2020-000151.

14.

Angelidi et al., Mayo Clinic Proceedings, doi:10.1016/j.mayocp.2021.01.001, Vitamin D Status is Associated With In-hospital Mortality and Mechanical Ventilation: A Cohort of COVID-19 Hospitalized Patients, https://www.sciencedirect.com/scie../article/abs/pii/S002561962100001X.

15.

Anglemyer et al., Cochrane Database of Systematic Reviews 2014, Issue 4, doi:10.1002/14651858.MR000034.pub2, Healthcare outcomes assessed with observational study designs compared with those assessed in randomized trials, https://www.cochranelibrary.com/cd..0.1002/14651858.MR000034.pub2/full.

16.

Annweiler et al., Nutrients, doi:10.3390/nu12113377, Vitamin D Supplementation Associated to Better Survival in Hospitalized Frail Elderly COVID-19 Patients: The GERIA-COVID Quasi-Experimental Study, https://www.mdpi.com/2072-6643/12/11/3377.

17.

Annweiler (B) et al., The Journal of Steroid Biochemistry and Molecular Biology, doi:10.1016/j.jsbmb.2020.105771, Vitamin D and survival in COVID-19 patients: A quasi-experimental study, https://www.sciencedirect.com/science/article/pii/S096007602030296X.

18.

Annweiler (C) et al., Nutrients, doi:10.3390/nu12113377, Vitamin D Supplementation Associated to Better Survival in Hospitalized Frail Elderly COVID-19 Patients: The GERIA-COVID Quasi-Experimental Study, https://www.mdpi.com/2072-6643/12/11/3377.

19.

Arroyo-Díaz et al., Frontiers in Public Health, doi:10.3389/fpubh.2021.758347, Previous Vitamin D Supplementation and Morbidity and Mortality Outcomes in People Hospitalised for COVID19: A Cross-Sectional Study, https://www.frontiersin.org/articles/10.3389/fpubh.2021.758347/full.

20.

Asgari et al., Acta Medica Iranica, doi:10.18502/acta.v59i11.7779, Vitamin D Insufficiency in Disease Severity and Prognosis of the Patients With SARS Corona Virus-2 Infection, https://acta.tums.ac.ir/index.php/acta/article/view/9507.

21.

Asghar et al., Am. J. Trop. Med. Hyg., doi:10.4269/ajtmh.21-0577, Evaluation of Vitamin-D Status and Its Association with Clinical Outcomes Among COVID-19 Patients in Pakistan, https://www.ajtmh.org/view/journal../article-10.4269-ajtmh.21-0577.xml.

22.

Asimi et al., Endocrine Abstracts, doi:10.1530/endoabs.73.PEP14.2, Selenium, zinc, and vitamin D supplementation affect the clinical course of COVID-19 infection in Hashimoto’s thyroiditis, https://www.endocrine-abstracts.org/ea/0073/ea0073pep14.2.

23.

Assiri et al., Journal of Infection and Public Health, doi:10.1016/j.jiph.2021.08.030, COVID-19 related treatment and outcomes among COVID-19 ICU patients: A retrospective cohort study, https://www.sciencedirect.com/science/article/pii/S1876034121002495.

24.

Atanasovska et al., Redox Report, doi:10.1080/13510002.2021.1999126 , Vitamin D levels and oxidative stress markers in patients hospitalized with COVID-19, https://www.tandfonline.com/doi/full/10.1080/13510002.2021.1999126.

25.

Bagheri et al., Journal of Family & Reproductive Health, doi:10.18502/jfrh.v14i3.4668 , Supplement Usage Pattern in a Group of COVID- 19 Patients in Tehran, https://europepmc.org/article/PMC/PMC7868648.

26.

Baktash et al., Postgraduate Medical Journal, doi:10.1136/postgradmedj-2020-138712, Vitamin D status and outcomes for hospitalised older patients with COVID-19, https://pmj.bmj.com/content/early/../06/postgradmedj-2020-138712?rss=1.

27.

Barassi et al., Panminerva Med., doi:10.23736/S0031-0808.21.04277-4, Vitamin D in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patients with non-invasive ventilation support, https://www.minervamedica.it/en/jo..ticle.php?cod=R41Y9999N00A21012508.

28.

Basaran et al., Bratislava Medical Journal, doi:10.4149/bll_2021_034, The relationship between vitamin D and the severity of COVID-19, http://www.elis.sk/index.php?page=..n=com_virtuemart&vmcchk=1&Itemid=1.

29.

Bayramoğlu et al., European Journal of Pediatrics, doi:10.1007/s00431-021-04030-1, The association between vitamin D levels and the clinical severity and inflammation markers in pediatric COVID-19 patients: single-center experience from a pandemic hospital, https://link.springer.com/article/10.1007/s00431-021-04030-1.

30.

Beigmohammadi et al., Trials, doi:10.1186/s13063-021-05795-4, The effect of supplementation with vitamins A, B, C, D, and E on disease severity and inflammatory responses in patients with COVID-19: a randomized clinical trial, https://link.springer.com/article/..6/s13063-021-05795-4/fulltext.html.

31.

Bennouar et al., Journal of the American College of Nutrition, doi:10.1080/07315724.2020.1856013, Vitamin D Deficiency and Low Serum Calcium as Predictors of Poor Prognosis in Patients with Severe COVID-19, https://www.tandfonline.com/doi/full/10.1080/07315724.2020.1856013.

32.

Bianconi et al., Nutrition, doi:10.1016/j.nut.2021.111408, Prevalence of vitamin D deficiency and its prognostic impact on patients hospitalized with COVID-19, https://www.sciencedirect.com/science/article/pii/S0899900721002707.

33.

Blanch-Rubió et al., Aging, doi:10.18632/aging.104117, Influence of anti-osteoporosis treatments on the incidence of COVID-19 in patients with non-inflammatory rheumatic conditions, https://www.aging-us.com/article/104117/text.

34.

Burahee et al., SICOT-J, doi:10.1051/sicotj/2021001, Older patients with proximal femur fractures and SARS-CoV-2 infection – An observational study, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7888253/#!po=1.28205.

35.

Butler-Laporte et al., PLOS Medicine, doi:10.1371/journal.pmed.1003605, Vitamin D and COVID-19 susceptibility and severity in the COVID-19 Host Genetics Initiative: A Mendelian randomization study, https://journals.plos.org/plosmedi..le?id=10.1371/journal.pmed.1003605.

36.

Campi et al., BMC Infectious Diseases, doi:10.1186/s12879-021-06281-7, Vitamin D and COVID-19 severity and related mortality: a prospective study in Italy, https://bmcinfectdis.biomedcentral..rticles/10.1186/s12879-021-06281-7.

37.

Cangiano et al., Aging, doi:10.18632/aging.202307, Mortality in an Italian nursing home during COVID-19 pandemic: correlation with gender, age, ADL, vitamin D supplementation, and limitations of the diagnostic tests, https://www.aging-us.com/article/202307/text.

38.

Carlberg et al., The Journal of Steroid Biochemistry and Molecular Biology, doi:10.1016/j.jsbmb.2018.01.002, In vivo response of the human epigenome to vitamin D: A Proof-of-principle study, https://www.sciencedirect.com/scie../article/abs/pii/S0960076018300037.

39.

Carpagnano et al., J. Endocrinol. Invest., 2020, Aug 9, 1-7, doi:10.1007/s40618-020-01370-x, Vitamin D deficiency as a predictor of poor prognosis in patients with acute respiratory failure due to COVID-19, https://link.springer.com/article/10.1007/s40618-020-01370-x.

40.

Castillo et al., Journal of Steroid Biochemistry and Molecular Biology, 203, October 2020, doi:10.1016/j.jsbmb.2020.105751, Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study, https://www.sciencedirect.com/science/article/pii/S0960076020302764.

41.

Cereda et al., Clinical Nutrition (Edinburgh, Scotland), doi:10.1016/j.clnu.2020.10.055, Vitamin D 25OH deficiency in COVID-19 patients admitted to a tertiary referral hospital, https://europepmc.org/article/med/33187772.

42.

Cereda (B) et al., Nutrition, doi:10.1016/j.nut.2020.111055, Vitamin D supplementation and outcomes in coronavirus disease 2019 (COVID-19) patients from the outbreak area of Lombardy, Italy, https://www.sciencedirect.com/science/article/pii/S0899900720303385.

43.

Charoenngam et al., Endocrine Practice, doi:10.1016/j.eprac.2021.02.013, Association of vitamin D status with hospital morbidity and mortality in adult hospitalized COVID-19 patients, https://www.endocrinepractice.org/..cle/S1530-891X(21)00057-4/fulltext.

44.

Chiodini et al., Frontiers in Public Health, doi:10.3389/fpubh.2021.736665, Vitamin D Status and SARS-CoV-2 Infection and COVID-19 Clinical Outcomes, https://www.frontiersin.org/articles/10.3389/fpubh.2021.736665/full.

45.

Chodick et al., Journal of Travel Medicine, doi:10.1093/jtm/taaa069, Angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers are not associated with increased risk of SARS-CoV-2 infection, https://academic.oup.com/jtm/article/27/5/taaa069/5836963?login=true.

46.

Concato et al., NEJM, 342:1887-1892, doi:10.1056/NEJM200006223422507, https://www.nejm.org/doi/full/10.1056/nejm200006223422507.

47.

Cozier et al., PLoS ONE, doi:10.1371/journal.pone.0255132, Lower serum 25(OH)D levels associated with higher risk of COVID-19 infection in U.S. Black women, https://journals.plos.org/plosone/..le?id=10.1371/journal.pone.0255132.

48.

D'Avolio et al., Nutrients, 12:5, 1–7, doi:10.3390/nu12051359, 25-hydroxyvitamin D concentrations are lower in patients with positive PCR for SARS-CoV-2, https://www.mdpi.com/2072-6643/12/5/1359.

49.

De Smet et al., American Journal of Clinical Pathology, doi:10.1093/ajcp/aqaa252, Serum 25(OH)D Level on Hospital Admission Associated With COVID-19 Stage and Mortality, https://academic.oup.com/ajcp/adva..e/doi/10.1093/ajcp/aqaa252/6000689.

50.

Deaton et al., Social Science & Medicine, 210, doi:10.1016/j.socscimed.2017.12.005, Understanding and misunderstanding randomized controlled trials, https://www.sciencedirect.com/science/article/pii/S0277953617307359.

51.

Demir et al., Journal of Medical Virology, doi:10.1002/jmv.26832, Vitamin D deficiency is associated with COVID‐19 positivity and the severity of the disease, https://onlinelibrary.wiley.com/doi/10.1002/jmv.26832.

52.

Deng, H., PyMeta, Python module for meta-analysis, http://www.pymeta.com/.

53.

Derakhshanian et al., Food Science & Nutrition, doi:10.1002/fsn3.2591, The predictive power of serum vitamin D for poor outcomes in COVID-19 patients, https://onlinelibrary.wiley.com/doi/full/10.1002/fsn3.2591.

54.

Desai et al., Open Forum Infectious Diseases, doi:10.1093/ofid/ofab408, Vitamin K & D Deficiencies Are Independently Associated With COVID-19 Disease Severity, https://academic.oup.com/ofid/article/8/10/ofab408/6330610.

55.

di Filippo et al, The Journal of Clinical Endocrinology & Metabolism, doi:10.1210/clinem/dgab599 , Vitamin D levels associate with blood glucose and BMI in COVID-19 patients predicting disease severity, https://academic.oup.com/jcem/adva..doi/10.1210/clinem/dgab599/6349205.

56.

Diaz-Curiel, Journal of Steroid Biochemistry and Molecular Biology, doi:10.1016/j.jsbmb.2021.105928, The relationship between 25(OH) vitamin D levels and COVID-19 onset and disease course in Spanish patients, https://www.sciencedirect.com/science/article/pii/S0960076021001217.

57.

Dror et al., medRxiv, doi:10.1101/2021.06.04.21258358, Pre-infection 25-hydroxyvitamin D3 levels and association with severity of COVID-19 illness, https://www.medrxiv.org/content/10.1101/2021.06.04.21258358v1.

58.

Dudley et al., BJPsych Bulletin, doi:10.1192/bjb.2021.55, Revisiting vitamin D status and supplementation for in-patients with intellectual and developmental disability in the North of England, UK, https://www.cambridge.org/core/jou..k/9ABB85B839DD2343107CCD98B10A81EA.

59.

Eden et al., BMJ Nutrition, Prevention & Health, doi:10.1136/bmjnph-2021-000270, Nutritional parameters and outcomes in patients admitted to intensive care with COVID-19: a retrospective single-centre service evaluation, https://nutrition.bmj.com/content/early/2021/08/10/bmjnph-2021-000270.

60.

Efird et al., International Journal of Environmental Research and Public Health, doi:10.3390/ijerph19010447, The Interaction of Vitamin D and Corticosteroids: A Mortality Analysis of 26,508 Veterans Who Tested Positive for SARS-CoV-2, https://www.mdpi.com/1660-4601/19/1/447/html.

61.

Elamir et al., Bone, doi:10.1016/j.bone.2021.116175, A Randomized Pilot Study Using Calcitriol in Hospitalized Patients, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425676/.

62.

Ersöz et al., International Journal of Clinical Practice, doi:10.1111/ijcp.14078, The association between micronutrient and hemogram values and prognostic factors in COVID-19 patients: A single-center experience from Turkey, https://onlinelibrary.wiley.com/doi/pdf/10.1111/ijcp.14078.

63.

Espitia-Hernandez et al., Biomedical Research, 31:5, Effects of Ivermectin-azithromycin-cholecalciferol combined therapy on COVID-19 infected patients: A proof of concept study, https://www.biomedres.info/biomedi..-proof-of-concept-study-14435.html.

64.

Faniyi et al., medRxiv, doi:10.1101/2020.10.05.20206706, Vitamin D status and seroconversion for COVID-19 in UK healthcare workers who isolated for COVID-19 like symptoms during the 2020 pandemic, https://www.medrxiv.org/content/10.1101/2020.10.05.20206706v1.

65.

Fasano et al., Movement Disorders, doi:10.1002/mds.28176, COVID-19 in Parkinson’s Disease Patients Living in Lombardy, Italy, https://movementdisorders.onlineli..ry.wiley.com/doi/10.1002/mds.28176.

66.

Fatemi et al., Acute and Critical Care, doi:10.4266/acc.2021.00605, Association of vitamin D deficiency with COVID-19 severity and mortality in Iranian people: a prospective observational study, http://accjournal.org/journal/view.php?doi=10.4266/acc.2021.00605.

67.

Faul et al., Irish Medical Journal, 113:5, 84, Vitamin D Deficiency and ARDS after SARS-CoV-2 Infection, http://imj.ie/vitamin-d-deficiency..d-ards-after-sars-cov-2-infection/.

68.

Freitas et al., medRxiv, doi:10.1101/2021.03.22.21254032, Vitamin D-related polymorphisms and vitamin D levels as risk biomarkers of COVID-19 infection severity, https://www.medrxiv.org/content/10.1101/2021.03.22.21254032v1.

69.

Galaznik et al., Journal of Clinical Oncology, doi:10.1200/JCO.2021.39.15_suppl.6589, Assessment of vitamin D deficiency and COVID-19 diagnosis in patients with breast or prostate cancer using electronic medical records, https://ascopubs.org/doi/abs/10.1200/JCO.2021.39.15_suppl.6589.

70.

Gaudio et al., International Journal of Environmental Research and Public Health, doi:10.3390/ijerph18073491, Vitamin D Levels Are Reduced at the Time of Hospital Admission in Sicilian SARS-CoV-2-Positive Patients, https://www.mdpi.com/1660-4601/18/7/3491.

71.

Gavioli et al., Journal of the American College of Nutrition, doi:10.1080/07315724.2020.1869626, An Evaluation of Serum 25-Hydroxy Vitamin D Levels in Patients with COVID-19 in New York City, https://www.tandfonline.com/doi/full/10.1080/07315724.2020.1869626.

72.

Giannini et al., Nutrients, doi:10.3390/nu13010219 , Effectiveness of In-Hospital Cholecalciferol Use on Clinical Outcomes in Comorbid COVID-19 Patients: A Hypothesis-Generating Study, https://www.mdpi.com/2072-6643/13/1/219/htm.

73.

Golabi et al., Nutrients, doi:10.3390/nu13103368 (preprint 8/26/2021), The Association between Vitamin D and Zinc Status and the Progression of Clinical Symptoms among Outpatients Infected with SARS-CoV-2 and Potentially Non-Infected Participants: A Cross-Sectional Study, https://www.mdpi.com/2072-6643/13/10/3368.

74.

Golabi (B) et al., Nutrients, doi:10.3390/nu13103368 (preprint 8/26/2021), The Association between Vitamin D and Zinc Status and the Progression of Clinical Symptoms among Outpatients Infected with SARS-CoV-2 and Potentially Non-Infected Participants: A Cross-Sectional Study, https://www.mdpi.com/2072-6643/13/10/3368.

75.

Gönen et al., Nutrients, doi:10.3390/nu13114047, Rapid and Effective Vitamin D Supplementation May Present Better Clinical Outcomes in COVID-19 (SARS-CoV-2) Patients by Altering Serum INOS1, IL1B, IFNg, Cathelicidin-LL37, and ICAM1, https://www.mdpi.com/2072-6643/13/11/4047.

76.

Güven et al, European Journal of Clinical Nutrition, doi:10.1038/s41430-021-00984-5, The effect of high-dose parenteral vitamin D3 on COVID-19-related inhospital mortality in critical COVID-19 patients during intensive care unit admission: an observational cohort study, https://www.nature.com/articles/s41430-021-00984-5.

77.

Hastie et al., Diabetes and Metabolic Syndrome: Clinical Research and Reviews, 14:4, 561–565, doi:10.1016/j.dsx.2020.04.050, Vitamin D concentrations and COVID-19 infection in UK Biobank, https://www.sciencedirect.com/scie../article/abs/pii/S1871402120301156.

78.

Hernández et al., The Journal of Clinical Endocrinology & Metabolism, doi:10.1210/clinem/dgaa733, Vitamin D Status in Hospitalized Patients with SARS-CoV-2 Infection, https://academic.oup.com/jcem/adva..doi/10.1210/clinem/dgaa733/5934827.

79.

Hernández (B) et al., The Journal of Clinical Endocrinology & Metabolism, doi:10.1210/clinem/dgaa733, Vitamin D Status in Hospitalized Patients with SARS-CoV-2 Infection, https://academic.oup.com/jcem/adva..doi/10.1210/clinem/dgaa733/5934827.

80.

Holt et al., medRxiv, doi:10.1101/2021.03.27.21254452, Risk factors for developing COVID-19: a population-based longitudinal study (COVIDENCE UK), https://www.medrxiv.org/content/10.1101/2021.03.27.21254452v2.

81.

Hurst et al., BMJ Open, doi:10.1136/bmjopen-2021-055435, Vitamin D insufficiency in COVID-19 and influenza A, and critical illness survivors: a cross-sectional study, https://bmjopen.bmj.com/content/11/10/e055435.long.

82.

Im et al., Int. J. Infect. Dis., doi:10.1016/j.ijid.2020.08.018, Nutritional status of patients with COVID-19, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418699/.

83.

Infante et al., Journal of the American College of Nutrition, doi:10.1080/07315724.2021.1877580, Low Vitamin D Status at Admission as a Risk Factor for Poor Survival in Hospitalized Patients With COVID-19: An Italian Retrospective Study, https://www.tandfonline.com/doi/full/10.1080/07315724.2021.1877580.

84.

Israel et al., medRxiv, doi:https://www.medrxiv.org/content/10.1101/2020.09.04.20188268v1, The link between vitamin D deficiency and Covid-19 in a large population, https://www.medrxiv.org/content/10.1101/2020.09.04.20188268v1.

85.

Israel (B) et al., Epidemiology and Global Health Microbiology and Infectious Disease, doi:10.7554/eLife.68165, Identification of drugs associated with reduced severity of COVID-19: A case-control study in a large population, https://elifesciences.org/articles/68165.

86.

Jain et al., Nature, doi:10.1038/s41598-020-77093-z, Analysis of vitamin D level among asymptomatic and critically ill COVID-19 patients and its correlation with inflammatory markers, https://www.nature.com/articles/s41598-020-77093-z.

87.

Jayawardena et al., Diabetes & Metabolic Syndrome: Clinical Research & Reviews, doi:10.1016/j.dsx.2021.03.006, Impact of the vitamin D deficiency on COVID-19 infection and mortality in Asian countries, https://www.sciencedirect.com/science/article/pii/S1871402121000746.

88.

Jevalikar et al., Scientific Reports, doi:10.1038/s41598-021-85809-y (preprint 12/28), Lack of association of baseline 25-hydroxyvitamin D levels with disease severity and mortality in Indian patients hospitalized for COVID-19, https://www.nature.com/articles/s41598-021-85809-y.

89.

Jimenez et al., Nutrients, doi:10.3390/nu13082559, Mortality in Hemodialysis Patients with COVID-19, the Effect of Paricalcitol or Calcimimetics, https://www.mdpi.com/2072-6643/13/8/2559.

90.

Jude et al., Journal of Clinical Endocrinology & Metabolism, doi:10.1210/clinem/dgab439, Vitamin D deficiency is associated with higher hospitalisation risk from COVID-19: a retrospective case-control study, https://academic.oup.com/jcem/adva..doi/10.1210/clinem/dgab439/6303537.

91.

Karahan et al., J. Nutr. Health Aging, doi:10.1007/s12603-020-1479-0 , Impact of Serum 25(OH) Vitamin D Level on Mortality in Patients with COVID-19 in Turkey, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533663/.

92.

Karonova et al., Nutrients, doi:10.3390/nu13093021, Low 25(OH)D Level Is Associated with Severe Course and Poor Prognosis in COVID-19, https://www.mdpi.com/2072-6643/13/9/3021.

93.

Karonova (B) et al., Infectology, doi:10.22625/2072-6732-2020-12-3-21-27, Serum 25(oH)D level in patients with CoVID-19, https://journal.niidi.ru/jofin/article/view/1073?locale=en_US.

94.

Katz el al., Nutrition, doi:10.1016/j.nut.2020.111106, Increased risk for Covid-19 in patients with Vitamin D deficiency, https://www.sciencedirect.com/science/article/pii/S0899900720303890.

95.

Kaufman et al., PLOS One, doi:10.1371/journal.pone.0239252, SARS-CoV-2 positivity rates associated with circulating 25-hydroxyvitamin D levels, https://journals.plos.org/plosone/..le?id=10.1371/journal.pone.0239252.

96.

Kaur et al., Indian Journal of Clinical Practice, 32:6, Correlation of Vitamin D Levels with COVID-19 Severity and Outcome, https://ijcp.in/Admin/CMS/PDF/7.%20ClinicalStudy_2IJCP_Nov2021.pdf.

97.

Kerget el al., Tuberk Toraks, doi:10.5578/tt.70027, Evaluation of the relationship of serum vitamin D levels in COVID-19 patients with clinical course and prognosis, https://pubmed.ncbi.nlm.nih.gov/33295720/.

98.

Krishnan et al., J Clin Anesth., doi:10.1016/j.jclinane.2020.110005, Clinical comorbidities, characteristics, and outcomes of mechanically ventilated patients in the State of Michigan with SARS-CoV-2 pneumonia, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7369577/.

99.

Lakkireddy et al., Scientific Reports, doi:10.1038/s41598-021-90189-4 (preprint 2/23/21), Impact of daily high dose oral vitamin D therapy on the inflammatory markers in patients with COVID 19 disease, https://www.nature.com/articles/s41598-021-90189-4.

100.

Lau et al., medRxiv, doi:10.1101/2020.04.24.20075838, Vitamin D Insufficiency is Prevalent in Severe COVID-19, https://www.medrxiv.org/content/10.1101/2020.04.24.20075838v1.

101.

Lázaro et al., Endocrine Abstracts, doi:10.1530/endoabs.70.EP552, Vitamin D deficit in type 2 diabetes patients during COVID-19 lockdown with and without supplementation, https://www.endocrine-abstracts.org/ea/0070/ea0070ep552.

102.

Leal et al., SSRN, doi:10.2139/ssrn.3949424 , Effect of a Nutritional Support System to Increase Survival and Reduce Mortality in Patients with COVID-19 in Stage III and Comorbidities: A Blinded Randomized Controlled Clinical Trial, https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3949424.

103.

Lee et al., Arch Intern Med., 2011, 171:1, 18-22, doi:10.1001/archinternmed.2010.482, Analysis of Overall Level of Evidence Behind Infectious Diseases Society of America Practice Guidelines, https://jamanetwork.com/journals/j..nternalmedicine/fullarticle/226373.

104.

Levitus et al., Journal of the Endocrine Society, doi: 10.1210/jendso/bvab048.567, The Effect of Vitamin D Supplementation on Severe COVID-19 Outcomes in Patients With Vitamin D Insufficiency, https://academic.oup.com/jes/article/5/Supplement_1/A279/6240740.

105.

Li et al., JAMA Network Open, doi:10.1001/jamanetworkopen.2021.11634, Assessment of the Association of Vitamin D Level With SARS-CoV-2 Seropositivity Among Working-Age Adults, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2779952.

106.

Li (B) et al., Aging and Disease, doi:10.14336/AD.2020.1108, Metabolic Healthy Obesity, Vitamin D Status, and Risk of COVID-19, http://www.aginganddisease.org/EN/10.14336/AD.2020.1108.

107.

Ling et el., Nutrients, doi:10.3390/nu12123799, High-Dose Cholecalciferol Booster Therapy is Associated with a Reduced Risk of Mortality in Patients with COVID-19: A Cross-Sectional Multi-Centre Observational Study, https://www.mdpi.com/2072-6643/12/12/3799.

108.

Livingston et al., Int. J. Clinical Practive, doi:10.1111/ijcp.14166, Detectable respiratory SARS‐CoV‐2 RNA is associated with low vitamin D levels and high social deprivation, https://onlinelibrary.wiley.com/doi/10.1111/ijcp.14166.

109.

Lohia et al., American Journal of Physiology-Endocrinology and Metabolism, doi:10.1152/ajpendo.00517.2020, Exploring the link between vitamin D and clinical outcomes in COVID-19, https://journals.physiology.org/doi/full/10.1152/ajpendo.00517.2020.

110.

Lohia (B) et al., American Journal of Physiology-Endocrinology and Metabolism, doi:10.1152/ajpendo.00517.2020, Exploring the link between vitamin D and clinical outcomes in COVID-19, https://journals.physiology.org/doi/full/10.1152/ajpendo.00517.2020.

111.

Louca et al., BMJ Nutrition, Prevention & Health, doi:10.1136/bmjnph-2021-000250 (preprint 11/30/20), Modest effects of dietary supplements during the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom Study app, https://nutrition.bmj.com/content/4/1/149.

112.

Loucera et al., Scientific Reports, doi:10.1038/s41598-021-02701-5 (preprint 4/29/21), Real world evidence of calcifediol or vitamin D prescription and mortality rate of COVID-19 in a retrospective cohort of hospitalized Andalusian patients, https://www.nature.com/articles/s41598-021-02701-5.

113.

Luo et al., The Journal of Nutrition, doi:10.1093/jn/nxaa332, Vitamin D Deficiency Is Inversely Associated with COVID-19 Incidence and Disease Severity in Chinese People, https://academic.oup.com/jn/advanc..cle/doi/10.1093/jn/nxaa332/5981721.

114.

Ma et al., The American Journal of Clinical Nutrition, doi:10.1093/ajcn/nqab389, Associations between predicted vitamin D status, vitamin D intake, and risk of SARS-CoV-2 infection and Coronavirus Disease 2019 severity, https://academic.oup.com/ajcn/adva..e/doi/10.1093/ajcn/nqab389/6448988.

115.

Ma (B) et al., The American Journal of Clinical Nutrition, doi:10.1093/ajcn/nqaa381, Habitual use of vitamin D supplements and risk of coronavirus disease 2019 (COVID-19) infection: a prospective study in UK Biobank, https://academic.oup.com/ajcn/adva..e/doi/10.1093/ajcn/nqaa381/6123965.

116.

Macaya et al., Nutr. Hosp., doi:10.20960/nh.03193, Interaction between age and vitamin D deficiency in severe COVID-19 infection, https://www.nutricionhospitalaria.org/articles/03193/show.

117.

Maghbooli et al., PLOS One, doi:10.1371/journal.pone.0239799, Vitamin D sufficiency, a serum 25-hydroxyvitamin D at least 30 ng/mL reduced risk for adverse clinical outcomes in patients with COVID-19 infection, https://journals.plos.org/plosone/..le?id=10.1371/journal.pone.0239799.

118.

Maghbooli (B) et al., Endocrine Practice, doi:10.1016/j.eprac.2021.09.016, Treatment with 25-hydroxyvitamin D3 (calcifediol) is associated with a reduction in the blood neutrophil-to-lymphocyte ratio marker of disease severity in patients hospitalized with COVID-19: a pilot, multicenter, randomized, placebo-controlled double blind clinical trial, https://www.sciencedirect.com/scie../article/abs/pii/S1530891X21012593.

119.

Mardani et al., Virus Research, doi:10.1016/j.virusres.2020.198148, Association of vitamin D with the modulation of the disease severity in COVID-19, https://www.sciencedirect.com/scie../article/abs/pii/S0168170220310558.

120.

Marik et al., Med Drug Discov., doi:10.1016/j.medidd.2020.100041, Does vitamin D status impact mortality from SARS-CoV-2 infection?, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7189189/.

121.

Martens et al., Nutrients, doi:10.3390/nu12051248, Vitamin D’s Effect on Immune Function, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7281985/.

122.

Matin et al., Archives of Microbiology, doi:10.1007/s00203-021-02482-5, The sufficient vitamin D and albumin level have a protective effect on COVID-19 infection, https://link.springer.com/article/10.1007/s00203-021-02482-5.

123.

Mazziotti et al., J Endocrinol. Invest., doi:10.1007/s40618-021-01535-2, Vitamin D deficiency, secondary hyperparathyroidism and respiratory insufficiency in hospitalized patients with COVID-19, https://link.springer.com/article/10.1007/s40618-021-01535-2.

124.

McLean et al., Open Forum Infect. Dis. September 2015, 2:3, doi:10.1093/ofid/ofv100, Impact of Late Oseltamivir Treatment on Influenza Symptoms in the Outpatient Setting: Results of a Randomized Trial, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525010/.

125.

Meltzer et al., JAMA Netw Open., doi:10.1001/jamanetworkopen.2021.4117, Association of Vitamin D Levels, Race/Ethnicity, and Clinical Characteristics With COVID-19 Test Results, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2777682.

126.

Meltzer (B) et al., JAMA network open, 3:9, doi:10.1001/jamanetworkopen.2020.19722, Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2770157.

127.

Meltzer (C) et al., JAMA Netw Open., doi:10.1001/jamanetworkopen.2021.4117, Association of Vitamin D Levels, Race/Ethnicity, and Clinical Characteristics With COVID-19 Test Results, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2777682.

128.

Mendy et al., medRxiv, doi:10.1101/2020.06.25.20137323, Factors Associated with Hospitalization and Disease Severity in a Racially and Ethnically Diverse Population of COVID-19 Patients, https://www.medrxiv.org/content/10.1101/2020.06.25.20137323v2.

129.

Merzon et al., The FEBS Journal, doi:doi.org/10.1111/febs.15495, Low plasma 25(OH) vitamin D level is associated with increased risk of COVID‐19 infection: an Israeli population‐based study, https://febs.onlinelibrary.wiley.com/doi/full/10.1111/febs.15495.

130.

Mohseni et al., Nutrition & Food Science, doi:10.1108/NFS-11-2020-0421, Do body mass index (BMI) and history of nutritional supplementation play a role in the severity of COVID-19? A retrospective study, https://www.emerald.com/insight/co..10.1108/NFS-11-2020-0421/full/html.

131.

Murai et al., JAMA, doi:10.1001/jama.2020.26848 (preprint 11/17), Effect of a Single High Dose of Vitamin D3 on Hospital Length of Stay in Patients With Moderate to Severe COVID-19: A Randomized Clinical Trial, https://jamanetwork.com/journals/jama/fullarticle/2776738.

132.

Nichol et al., Injury, 2010, doi: 10.1016/j.injury.2010.03.033, Challenging issues in randomised controlled trials, https://www.injuryjournal.com/article/S0020-1383(10)00233-0/fulltext.

133.

Nimavat et al., Annals of Medicine and Surgery, doi:10.1016/j.amsu.2021.102661, Vitamin D deficiency and COVID-19: A case-control study at a tertiary care hospital in India, https://www.sciencedirect.com/science/article/pii/S2049080121006117.

134.

Nogués et al., The Journal of Clinical Endocrinology & Metabolism, doi:10.1210/clinem/dgab405 , Calcifediol Treatment and COVID-19-Related Outcomes, https://academic.oup.com/jcem/adva..doi/10.1210/clinem/dgab405/6294179.

135.

Orchard et al., Clin Chem Lab Med, doi:10.1515/cclm-2020-1567, Vitamin-D levels and intensive care unit outcomes of a cohort of critically ill COVID-19 patients, https://www.degruyter.com/document/doi/10.1515/cclm-2020-1567/html.

136.

Oristrell et al., Journal of Endocrinological Investigation, doi:10.1007/s40618-021-01639-9, Vitamin D supplementation and COVID-19 risk: a population-based, cohort study, https://link.springer.com/article/10.1007/s40618-021-01639-9.

137.

Oristrell (B) et al., Biomedicines, doi:10.3390/biomedicines9050509 (preprint 4/6/21), Association of Calcitriol Supplementation with Reduced COVID-19 Mortality in Patients with Chronic Kidney Disease: A Population-based Study, https://www.mdpi.com/2227-9059/9/5/509.

138.

Panagiotou et al., medRxiv, doi:10.1101/2020.06.21.20136903, Low serum 25-hydroxyvitamin D (25[OH]D) levels in patients hospitalised with COVID-19 are associated with greater disease severity: results of a local audit of practice, https://www.medrxiv.org/content/10.1101/2020.06.21.20136903v2.

139.

Papadimitriou et al., World J. Virology, doi:10.5501/wjv.v10.i3.111], Association between population vitamin D status and SARS-CoV-2 related serious-critical illness and deaths: An ecological integrative approach, https://www.wjgnet.com/2220-3249/full/v10/i3/111.htm.

140.

Parra-Ortega et al., Nutrition Research and Practice, doi:10.4162/nrp.2021.15.S1.S32, 25-Hydroxyvitamin D level is associated with mortality in patients with critical COVID-19: a prospective observational study in Mexico City, https://e-nrp.org/DOIx.php?id=10.4162/nrp.2021.15.S1.S32.

141.

Pecina et al., Journal of Primary Care & Community Health, doi:10.1177/21501327211041206 , Vitamin D Status and Severe COVID-19 Disease Outcomes in Hospitalized Patients, https://journals.sagepub.com/doi/full/10.1177/21501327211041206.

142.

Pepkowitz et al., Research Square, doi:10.21203/rs.3.rs-83262/v1, Vitamin D Deficiency is Associated with Increased COVID-19 Severity: Prospective Screening of At-Risk Groups is Medically Indicated, https://www.researchsquare.com/article/rs-83262/v1.

143.

Pimental et al., Clinical Nutrition ESPEN, doi:10.1016/j.clnesp.2021.05.021, Low vitamin D levels and increased neutrophil in patients admitted at ICU with COVID-19, https://clinicalnutritionespen.com..cle/S2405-4577(21)00201-1/fulltext.

144.

Putra et al., European Journal of Medical and Health Sciences, doi:10.24018/ejmed.2021.3.6.1131, Vitamin D Levels among Hospitalized and Non-Hospitalized COVID-19 Patients in Dr. M. Djamil General Hospital Padang, https://ej-med.org/index.php/ejmed/article/view/1131.

145.

Quraishi et al., JAMA Surgery, doi:10.1001/jamasurg.2013.3176, Association Between Preoperative 25-Hydroxyvitamin D Level and Hospital-Acquired Infections Following Roux-en-Y Gastric Bypass Surgery, https://jamanetwork.com/journals/jamasurgery/fullarticle/1782085.

146.

Radujkovic et al., Nutrients 2020, 12:9, 2757, doi:10.3390/nu12092757, Vitamin D Deficiency and Outcome of COVID-19 Patients, https://www.mdpi.com/2072-6643/12/9/2757/htm.

147.

Rafailia et al., medRxiv, doi:10.1101/2021.01.28.21250673, Is vitamin D deficiency associated with the COVID-19 epidemic in Europe, https://www.medrxiv.org/content/10.1101/2021.01.28.21250673v1.

148.

Raisi-Estabragh et al., J. Public Health, doi:10.1093/pubmed/fdaa095, Greater risk of severe COVID-19 in Black, Asian and Minority Ethnic populations is not explained by cardiometabolic, socioeconomic or behavioural factors, or by 25(OH)-vitamin D status: study of 1326 cases from the UK Biobank, https://academic.oup.com/jpubhealth/article/42/3/451/5859581.

149.

Ramirez-Sandoval et al., Archives of Medical Research, doi:10.1016/j.arcmed.2021.09.006, Very Low Vitamin D Levels are a Strong Independent Predictor of Mortality in Hospitalized Patients with Severe COVID-19, https://www.sciencedirect.com/scie../article/abs/pii/S0188440921001983.

150.

Rastogi et al., Postgraduate Medical Journal, doi:10.1136/postgradmedj-2020-139065, Short term, high-dose vitamin D supplementation for COVID-19 disease: a randomised, placebo-controlled, study (SHADE study), https://pmj.bmj.com/content/early/..1/12/postgradmedj-2020-139065.full.

151.

Rhodes et al., BMJ Nutr. Prev. Health, doi:10.1136/bmjnph-2020-000110, COVID-19 mortality increases with northerly latitude after adjustment for age suggesting a link with ultraviolet and vitamin D, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664496/.

152.

Ribeiro et al., Clinica Chimica Acta, doi:10.1016/j.cca.2021.08.003, Previous vitamin D status and total cholesterol are associated with SARS-CoV-2 infection, https://www.sciencedirect.com/scie..e/pii/S0009898121002709?via%3Dihub.

153.

Ricci et al., Respiratory Research, doi:10.1186/s12931-021-01666-3, Circulating Vitamin D levels status and clinical prognostic indices in COVID-19 patients, https://respiratory-research.biome..rticles/10.1186/s12931-021-01666-3.

154.

Sainz-Amo et al., Journal of Neurology, doi:10.1007/s00415-020-10272-0, COVID-19 in Parkinson’s disease: what holds the key?, https://link.springer.com/article/10.1007/s00415-020-10272-0.

155.

Sánchez-Zuno, J. Clinical Medicine, doi:10.3390/jcm10112378, Vitamin D Levels in COVID-19 Outpatients from Western Mexico: Clinical Correlation and Effect of Its Supplementation, https://www.mdpi.com/2077-0383/10/11/2378.

156.

Sánchez-Zuno (B), J. Clinical Medicine, doi:10.3390/jcm10112378, Vitamin D Levels in COVID-19 Outpatients from Western Mexico: Clinical Correlation and Effect of Its Supplementation, https://www.mdpi.com/2077-0383/10/11/2378.

157.

Savitri et al., Annals of the Romanian Society for Cell Biology, 25:6, Comparison between Vitamin D Level of Asymptomatic Confirmed Covid-19 Patients with Symptomatic Confirmed Covid-19 Patients in Makassar, https://www.annalsofrscb.ro/index.php/journal/article/view/9130.

158.

Seven et al., The Journal of Maternal-Fetal & Neonatal Medicine, doi:10.1080/14767058.2021.2005564, Correlation between 25-hydroxy vitamin D levels and COVID-19 severity in pregnant women: a cross-sectional study, https://www.tandfonline.com/doi/full/10.1080/14767058.2021.2005564.

159.

Silva et al., Nutrition Research, doi:10.1016/j.nutres.2014.12.008, Does serum 25-hydroxyvitamin D decrease during acute-phase response? A systematic review, https://www.sciencedirect.com/scie../article/abs/pii/S0271531714002875.

160.

Sinaci et al., The Journal of Steroid Biochemistry and Molecular Biology, doi:10.1016/j.jsbmb.2021.105964, Impact of vitamin D on the course of COVID-19 during pregnancy: A case control study, https://www.sciencedirect.com/science/article/pii/S0960076021001576.

161.

Soliman et al., Proceedings of Singapore Healthcare, doi:10.1177/20101058211041405, Impact of Vitamin D Therapy on the Progress COVID-19: Six Weeks Follow-Up Study of Vitamin D Deficient Elderly Diabetes Patients, https://journals.sagepub.com/doi/full/10.1177/20101058211041405.

162.

Sooriyaarachchi et al., Clinical Nutrition ESPEN, doi:10.1016/j.clnesp.2021.05.011, Impact of vitamin D deficiency on COVID-19, https://www.sciencedirect.com/science/article/pii/S2405457721001911.

163.

Sulli et al., Nutrients, doi:10.3390/nu13030717 , Vitamin D and Lung Outcomes in Elderly COVID-19 Patients, https://www.mdpi.com/2072-6643/13/3/717.

164.

Sulli (B) et al., Nutrients, doi:10.3390/nu13030717 , Vitamin D and Lung Outcomes in Elderly COVID-19 Patients, https://www.mdpi.com/2072-6643/13/3/717.

165.

Susianti et al., Journal of Medical Biochemistry, doi:10.5937/jomb0-30228 , Low levels of vitamin D were associated with coagulopathy among hospitalized coronavirus disease-19 (COVID-19) patients: A single-centered study in Indonesia, https://scindeks.ceon.rs/Article.aspx?artid=1452-82582104341S&lang=en.

166.

Sweeting et al., Statistics in Medicine, doi:10.1002/sim.1761, What to add to nothing? Use and avoidance of continuity corrections in meta‐analysis of sparse data, https://onlinelibrary.wiley.com/doi/10.1002/sim.1761.

167.

Szeto et al., Endocrine Research, doi:10.1080/07435800.2020.1867162, Vitamin D Status and COVID-19 Clinical Outcomes in Hospitalized Patients, https://www.tandfonline.com/doi/full/10.1080/07435800.2020.1867162.

168.

Tan et al., Nutrition, doi:10.1016/j.nut.2020.111017 (preprint 6/10/20), Cohort study to evaluate the effect of combination Vitamin D, Magnesium and Vitamin B12 (DMB) on progression to severe outcome in older COVID-19 patients, https://www.sciencedirect.com/science/article/pii/S0899900720303002.

169.

Tehrani et al., Clinical Nutrition, doi:10.1016/j.clnesp.2021.01.014, Evaluation of vitamin D levels in COVID-19 patients referred to Labafinejad hospital in Tehran and its relationship with disease severity and mortality, https://clinicalnutritionespen.com..cle/S2405-4577(21)00028-0/fulltext.

170.

Tomasa-Irriguible et al., Metabolites, doi:10.3390/metabo11090565 (preprint 10/26/2020), Low Levels of Few Micronutrients May Impact COVID-19 Disease Progression: An Observational Study on the First Wave, https://www.mdpi.com/2218-1989/11/9/565.

171.

Treanor et al., JAMA, 2000, 283:8, 1016-1024, doi:10.1001/jama.283.8.1016, Efficacy and Safety of the Oral Neuraminidase Inhibitor Oseltamivir in Treating Acute Influenza: A Randomized Controlled Trial, https://jamanetwork.com/journals/jama/fullarticle/192425.

172.

Ünsal et al., Journal of Endocrinological Investigation, doi:10.1007/s40618-021-01566-9, Retrospective analysis of vitamin D status on ınflammatory markers and course of the disease in patients with COVID-19 infection, https://link.springer.com/article/10.1007/s40618-021-01566-9.

173.

Ünsal (B) et al., Journal of Endocrinological Investigation, doi:10.1007/s40618-021-01566-9, Retrospective analysis of vitamin D status on ınflammatory markers and course of the disease in patients with COVID-19 infection, https://link.springer.com/article/10.1007/s40618-021-01566-9.

174.

Vanegas-Cedillo, medRxiv, doi:10.1101/2021.03.12.21253490, Serum Vitamin D levels are associated with increased COVID-19 severity markers and mortality independent of visceral adiposity, https://www.medrxiv.org/content/10.1101/2021.03.12.21253490v2.

175.

Vasheghani et al., Scientific Reports, doi:10.1038/s41598-021-97017-9 (preprint 1/18/2021), The relationship between serum 25-hydroxyvitamin D levels and the severity of COVID-19 disease and its mortality, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8413335/.

176.

Vasheghani (B) et al., Scientific Reports, doi:10.1038/s41598-021-97017-9 (preprint 1/18/2021), The relationship between serum 25-hydroxyvitamin D levels and the severity of COVID-19 disease and its mortality, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8413335/.

177.

Vassiliou et al., Hellenic Journal of Cardiology, doi:10.1016/j.hjc.2020.11.011, Vitamin D deficiency correlates with a reduced number of natural killer cells in intensive care unit (ICU) and non-ICU patients with COVID-19 pneumonia, https://www.sciencedirect.com/science/article/pii/S1109966620302840.

178.

Vassiliou (B) et al., Nutrients, doi:10.3390/nu12123773, Low 25-Hydroxyvitamin D Levels on Admission to the Intensive Care Unit May Predispose COVID-19 Pneumonia Patients to a Higher 28-Day Mortality Risk: A Pilot Study on a Greek ICU Cohort, https://www.mdpi.com/2072-6643/12/12/3773/htm.

179.

Walk et al., medRxiv, doi:10.1101/2020.11.07.20227512, Vitamin D - contrary to vitamin K - does not associate with clinical outcome in hospitalized COVID-19 patients, https://www.medrxiv.org/content/10.1101/2020.11.07.20227512v1.

180.

Walrand, S., Nature, doi:10.1038/s41598-021-81419-w, Autumn COVID-19 surge dates in Europe correlated to latitudes, not to temperature-humidity, pointing to vitamin D as contributing factor, https://www.nature.com/articles/s41598-021-81419-w.

181.

Yadav et al., Indian Journal of Clinical Biochemistry, doi:10.1007/s12291-020-00950-1, Association of Vitamin D Status with COVID-19 Infection and Mortality in the Asia Pacific region: A Cross-Sectional Study, https://link.springer.com/article/10.1007/s12291-020-00950-1.

182.

Ye et al., Journal of the American College of Nutrition, doi:10.1080/07315724.2020.182600, Does Serum Vitamin D Level Affect COVID-19 Infection and Its Severity? A Case-Control Study, https://www.tandfonline.com/doi/full/10.1080/07315724.2020.1826005.

183.

Yeh et al., BMJ, doi:10.1136/bmj.k5094 , Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial, https://www.bmj.com/content/363/bmj.k5094.

184.

Yildiz et al., Bratislava Medical Journal, doi:10.4149/BLL_2021_119, The prognostic significance of vitamin D deficiency in patients with COVID-19 pneumonia, http://www.elis.sk/index.php?page=..n=com_virtuemart&vmcchk=1&Itemid=1.

185.

Yılmaz et al., Pediatric Pulmonology, doi:10.1002/ppul.25106 , Is vitamin D deficiency a risk factor for COVID‐19 in children?, https://onlinelibrary.wiley.com/doi/10.1002/ppul.25106.

186.

Zelzer et al., Nutrients, doi:10.3390/nu13072129, Vitamin D Metabolites and Clinical Outcome in Hospitalized COVID-19 Patients, https://www.mdpi.com/2072-6643/13/7/2129.

187.

Zhang et al., JAMA, 80:19, 1690, doi:10.1001/jama.280.19.1690, What's the relative risk? A method of correcting the odds ratio in cohort studies of common outcomes, https://jamanetwork.com/journals/jama/fullarticle/188182.

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