Summary of COVID-19 vitamin D studies

1. Singh et al., Therapeutic high-dose vitamin D for vitamin D-deficient severe COVID-19 disease: randomized, double-blind, placebo-controlled study (SHADE-S)

90 patient vitamin D late treatment RCT: 45% lower mortality (p=0.05) and 40% improved recovery (p=0.01).
RCT 90 vitamin D deficient moderate/severe COVID-19 ARDS patients in India, showing lower mortality with vitamin D treatment. 600,000IU nanoformulation cholecalciferol.
May 2022, J. Public Health, https://academic.oup.com/jpubhealth/advance-article-abstract/doi/10.1093/pubmed/fdae007/7591923?redirectedFrom=fulltext&login=false, https://c19p.org/singh7

2. Sánchez-Zuno et al., Vitamin D Levels in COVID-19 Outpatients from Western Mexico: Clinical Correlation and Effect of Its Supplementation

42 patient vitamin D early treatment RCT: 89% lower severe cases (p=0.04) and 81% improved recovery (p=0.22).
Very small 42 PCR+ outpatient RCT in Mexico, 22 treated with vitamin D. Most patients had insufficient vitamin D levels, there were more symptoms in those with insufficient levels, and there were less cases with fever or with >3 symptoms at day 14 for treatment with vitamin D.
May 2021, Sánchez-Zuno, J. Clinical Medicine, https://www.mdpi.com/2077-0383/10/11/2378, https://c19p.org/sanchezzuno

3. Elamir et al., A Randomized Pilot Study Using Calcitriol in Hospitalized Patients

50 patient vitamin D late treatment RCT: 86% lower mortality (p=0.23), 38% lower ICU admission (p=0.33), 40% shorter hospitalization (p=0.14), and 86% improved recovery (p=0.03).
RCT 50 hospitalized patients in the USA, 25 treated with calcitriol, showing significantly improved oxygenation with treatment. Mortality, intubation, ICU admission, and hospitalization time also favored treatment, while not reaching statistical significance with the very small sample size.
Sep 2021, Bone, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425676/, https://c19p.org/elamir

4. De Niet et al., Positive Effects of Vitamin D Supplementation in Patients Hospitalized for COVID-19: A Randomized, Double-Blind, Placebo-Controlled Trial

43 patient vitamin D late treatment RCT: 45% faster recovery (p=0.06) and 50% shorter hospitalization (p=0.003).
RCT with 21 vitamin D and 22 placebo hospitalized patients in Belgium with vitamin D deficiency, showing significantly shorter hospitalization and improved clinical recovery with treatment.
Jul 2022, Nutrients, https://www.mdpi.com/2072-6643/14/15/3048, https://c19p.org/deniet

5. Villasis-Keever et al., Efficacy and Safety of Vitamin D Supplementation to Prevent COVID-19 in Frontline Healthcare Workers. A Randomized Clinical Trial

302 patient vitamin D prophylaxis RCT: 78% fewer cases (p=0.001).
RCT 321 healthcare workers in Mexico, showing significantly lower SARS-CoV-2 infection with vitamin D prophylaxis. 4,000IU daily for 30 days. In comparison to [Jolliffe], this study used a higher dose, the participants had much higher exposure to SARS-CoV-2 patients, and the study was prior to vaccination. In [Jolliffe], 89% of participants had received a vaccine dose by the end of the study period, and the period overlapped with increasing solar UVB. For more discussion see [twitter.com].
Apr 2022, Archives of Medical Research, https://www.sciencedirect.com/science/article/abs/pii/S0188440922000455, https://c19p.org/villasiskeever

6. Entrenas Castillo et al., 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

76 patient vitamin D late treatment RCT: 85% lower mortality (p=0.11) and 94% lower ICU admission (p=0.008).
RCT on calcifediol (25-hydroxyvitamin D) treatment for hospitalized COVID-19 patients showing significantly reduced intensive care unit admissions. All patients received standard care including HCQ+AZ. For additional analysis see Jungreis et al. [Jungreis].
Aug 2020, J. Steroid Biochemistry and Molecular Biology, 203, October 2020, https://www.sciencedirect.com/science/article/pii/S0960076020302764, https://c19p.org/entrenascastillo

7. Rastogi et al., Short term, high-dose vitamin D supplementation for COVID-19 disease: a randomised, placebo-controlled, study (SHADE study)

40 patient vitamin D late treatment RCT: 53% improved viral clearance (p=0.02).
53% reduction in PCR+ with high-dose cholecalciferol supplementation. RCT with 16 treatment patients and 24 control patients. 25(OH)D levels at day 14 were 52 ng/ml vs. 15 ng/ml in the intervention and control group.
Nov 2020, Postgraduate Medical J., https://pmj.bmj.com/content/early/2020/11/12/postgradmedj-2020-139065.full, https://c19p.org/rastogi

8. Sanz et al., Vitamin D3 supplementation in COVID-19 patients with cardiovascular disease and gut dysbiosis

22 patient vitamin D late treatment RCT: 83% lower ventilation (p=0.06) and 60% lower ICU admission (p=0.36).
Small RCT 22 hospitalized COVID-19 patients with cardiovascular disease in Argentina showing lower mortality, ventilation, and ICU admission with vitamin D treatment, without statistical significance. Treatment was associated with lower levels of inflammatory markers IL-6, IL-8 and TNF-α, higher levels of anti-inflammatory IL-10, and improvements in gut microbiome markers. 10,000 IU/day vitamin D3 for 10 days.
Jun 2024, Hipertensión y Riesgo Vascular, https://www.sciencedirect.com/science/article/pii/S1889183724000564, https://c19p.org/sanz

9. Comunale et al., Vitamin D Supplementation and Prior Oral Poliovirus Vaccination Decrease Odds of COVID-19 Outcomes among Adults Recently Inoculated with Inactivated Poliovirus Vaccine

282 patient vitamin D prophylaxis study: 91% fewer symptomatic cases (p=0.0006) and 88% fewer cases (p=0.001).
Retrospective 282 adults recently vaccinated against poliovirus showing vitamin D supplementation associated with lower COVID-19 PCR+ cases, lower symptomatic cases, and shorter duration of symptoms.
Jan 2024, Vaccines, https://www.mdpi.com/2076-393X/12/2/121, https://c19p.org/comunale

10. Nogués et al., Calcifediol Treatment and COVID-19-Related Outcomes

838 patient vitamin D late treatment study: 79% lower mortality (p=0.001) and 87% lower ICU admission (p<0.0001).
Quasi-randomized trial with 930 hospitalized patients, 447 treated with calcifediol, showing significantly lower ICU admission and death with treatment. Note that the randomization in this trial is by ward. Authors report that patients were allocated to empty beds available at admission time regardless of patient conditions, and that staff in all wards followed the same protocol. The earlier preprint for this article was censored by the Lancet. The Lancet reportedly requested a review from a Twitter user that posted negative comments [github.com]. The review provides useful feedback for the authors to improve the reporting of the cluster nature of the RCT, and to explain the delay in registration, however it is highly unusual to censor a preprint in this way. Authors responded to the issues raised here: [pubpeer.com]
Jan 2021, The J. Clinical Endocrinology & Metabolism , https://academic.oup.com/jcem/advance-article/doi/10.1210/clinem/dgab405/6294179, https://c19p.org/nogues

11. Fiore et al., Effectiveness of Vitamin D Supplements among Patients Hospitalized for COVID-19: Results from a Monocentric Matched-Cohort Study

116 patient vitamin D late treatment study: 93% lower mortality (p=0.02), 50% lower ventilation (p=0.36), 50% lower ICU admission (p=0.36), and 48% lower progression (p=0.04).
Retrospective 116 patients with D levels < 30ng/mL, 58 treated with vitamin D 100,000IU daily for two days, and 58 matched controls, showing significantly lower mortality with treatment.
May 2022, Healthcare, https://www.mdpi.com/2227-9032/10/5/956, https://c19p.org/fiore2

12. Oristrell et al., Association of Calcitriol Supplementation with Reduced COVID-19 Mortality in Patients with Chronic Kidney Disease: A Population-based Study

5,703 patient vitamin D prophylaxis study: 43% lower mortality (p=0.001), 43% lower severe cases (p=0.0008), and 22% fewer cases (p=0.01).
Retrospective study of calcitriol supplementation with chronic kidney disease patients in Catalonia showing lower cases, severe cases, and mortality with supplementation. A dose-response relationship was found for severe cases and mortality.
Apr 2021, Biomedicines, https://www.mdpi.com/2227-9059/9/5/509, https://c19p.org/oristrell

13. Campi et al., Vitamin D and COVID-19 severity and related mortality: a prospective study in Italy

155 patient vitamin D prophylaxis study: 88% lower severe cases (p<0.0001).
Prospective study of 103 hospitalized patients in Italy, showing very high prevalence of vitamin D deficiency, and increased severity for lower vitamin D levels. Vitamin D supplementation was significantly less common for cases.
Jun 2021, BMC Infectious Diseases, https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-021-06281-7, https://c19p.org/campi

14. Lakkireddy et al., Effect of Short Term High Dose Oral Vitamin D Therapy on the Inflammatory Markers in Patients with COVID 19 Disease

87 patient vitamin D late treatment RCT: 61% lower mortality (p=0.27), 22% lower ICU admission (p=0.74), and 7% shorter hospitalization (p=0.9).
RCT 44 treatment and 43 control patients with vitamin D levels <30ng/ml, showing significant reduction in inflammatory markers with treatment of 60,000IU vitamin D per day for 8 days (10 days for BMI >25). Death and ICU admission was lower in the treatment group but not statistically significant. Randomization was simple alternation, with the allocation officer unaware of which group patients were being assigned to as detailed in the study. An earlier version of this study was censored based on incorrect claims from an anti-treatment researcher. For discussion see [c19early.org].
Jul 2022, Archives of Clinical and Biomedical Research, https://www.fortunejournals.com/articles/effect-of-short-term-high-dose-oral-vitamin-d-therapy-on-the-inflammatory-markers-in-patients-with-covid-19-disease.html, https://c19p.org/lakkireddy

15. Bishop et al., REsCue Trial: Randomized Controlled Clinical Trial with Extended-Release Calcifediol in Symptomatic COVID-19 Outpatients

134 patient vitamin D late treatment RCT: 85% lower progression (p=0.25) and 34% improved recovery (p=0.56).
Small RCT with low-risk patients in the USA showing no significant differences in overall recovery. Minimal details on outcomes are provided in the preprint. Authors note significantly faster resolution of respiratory symptoms when treatment increased vitamin D levels. Baseline vitamin D was relatively high, mean 37±1 ng/mL, 95% >20ng/mL, leaving little room for improvement. Treatment delay is not specified but is likely relatively late based on the symptoms at baseline, PCR testing delay, and exclusion with FLU-PRO scores <1.5. ER/urgent care data from clinicaltrials.gov.
Feb 2022, Nutrition, https://www.sciencedirect.com/science/article/pii/S0899900722003100, https://c19p.org/bishop

16. Yildiz et al., The prognostic significance of vitamin D deficiency in patients with COVID-19 pneumonia

207 patient vitamin D late treatment study: 81% lower mortality (p=0.04), 94% lower ICU admission (p=0.13), and 10% shorter hospitalization (p=0.32).
Retrospective 207 hospitalized patients in Turkey, 37 with vitamin D levels <30ng/ml treated with a single dose of 300,000IU vitamin D, showing lower mortality with treatment.
Sep 2021, Bratislava Medical J., http://www.elis.sk/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=7390&category_id=171&option=com_virtuemart&vmcchk=1&Itemid=1, https://c19p.org/yildiz

17. Zurita-Cruz et al., Efficacy and safety of vitamin D supplementation in hospitalized COVID-19 pediatric patients: A randomized controlled trial

45 patient vitamin D late treatment RCT: 79% lower mortality (p=0.11), 72% lower ventilation (p=0.08), and 73% lower ICU admission (p=0.006).
RCT 45 hospitalized high-risk pediatric patients requiring supplemental oxygen in Mexico, showing lower mortality, ventilation, and intensive care with vitamin D treatment, however there were less severe and critical cases at baseline in the treatment group.
Jul 2022, Frontiers in Pediatrics, https://www.frontiersin.org/articles/10.3389/fped.2022.943529/full, https://c19p.org/zuritacruz

18. Karonova et al., Effect of Cholecalciferol Supplementation on the Clinical Features and Inflammatory Markers in Hospitalized COVID-19 Patients: A Randomized, Open-Label, Single-Center Study

110 patient vitamin D late treatment RCT: 86% lower ICU admission (p=0.11) and 7% lower need for oxygen therapy (p=0.85).
RCT with 56 cholecalciferol and 54 control hospitalized patients with vitamin D insufficiency or deficiency in Russia, showing positive effects on immune status. The median age in the treatment group was 7 years lower and deficiency was less common, while baseline treatment group CT lung involvement and supplemental oxygen use was higher in the treatment group. Treatment increased vitamin D levels and neutrophil and lymphocyte counts, decreased CRP levels, and was associated with a decrease in CD38++CD27 transitional and CD27−CD38+ mature naive B cells and an increase in CD27−CD38− DN B cells.
Jun 2022, Nutrients, https://www.mdpi.com/2072-6643/14/13/2602, https://c19p.org/karonova5

19. Leal-Martínez et al., 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

80 patient vitamin D late treatment RCT: 86% lower mortality (p=0.03) and 57% lower ventilation (p=0.31).
80 patient RCT with 40 patients treated with a comprehensive regimen of nutritional support, showing significantly lower mortality with treatment. Treatment contained cholecalciferol, vitamin C, zinc, spirulina maxima, folic acid, glutamine, vegetable protein, selenium, resveratrol, omega-3 fatty acids, l-arginine, magnesium, probiotics, and B-complex IV. Adherence was strictly monitored.
Oct 2021, Int. J. Environmental Research and Public Health, https://www.mdpi.com/1660-4601/19/3/1172/htm, https://c19p.org/lealmartinez

20. Jimenez et al., Mortality in Hemodialysis Patients with COVID-19, the Effect of Paricalcitol or Calcimimetics

285 patient vitamin D prophylaxis study: 50% lower mortality (p=0.02).
Retrospective 288 hemodialysis patients in Spain, 137 with existing vitamin D treatments (94 with paricalcitol), showing lower mortality with treatment. There was no significant difference in outcomes based on serum levels, however authors do not separate patients that received vitamin D treatment.
Jul 2021, Nutrients, https://www.mdpi.com/2072-6643/13/8/2559, https://c19p.org/jimenez

21. Baralić et al., Significance of 1,25-Dihydroxyvitamin D3 on Overall Mortality in Peritoneal Dialysis Patients with COVID-19

52 patient vitamin D prophylaxis study: 67% lower mortality (p=0.02).
Prospective analysis of 52 peritoneal dialysis patients, 31 on calcitriol (vitamin D) therapy. All patients tested positive for COVID-19 during followup (median 26 months). Mortality was significantly lower for patients on calcitriol therapy in univariate Cox regression analysis and in Kaplan-Meier analysis. Multivariate Cox regression analysis showed only diabetes mellitus with statistical significance.
Apr 2023, Nutrients, https://www.mdpi.com/2072-6643/15/9/2050, https://c19p.org/baralic

22. Şengül et al., Serum Vitamin D Concentrations and Covid-19 In Pregnant Women, Does Vitamin D Supplementation Impact Results? A Comprehensive Study

318 patient vitamin D prophylaxis study: 69% fewer cases (p=0.004).
Retrospective 318 pregnant women, 54 COVID+ and 264 healthy controls, showing lower risk of COVID-19 with vitamin D supplementation, and with higher vitamin D levels.
Dec 2022, Cukurova Anestezi ve Cerrahi Bilimler Dergisi, https://dergipark.org.tr/en/doi/10.36516/jocass.1185181, https://c19p.org/sengul

23. De Nicolò et al., Possible Impact of Vitamin D Status and Supplementation on SARS-CoV-2 Infection Risk and COVID-19 Symptoms in a Cohort of Patients with Inflammatory Bowel Disease

106 patient vitamin D prophylaxis study: 88% lower IgG positivity (p=0.002).
Prospective study of 106 IBD patients in Italy, showing lower risk of IgG positivity with vitamin D supplementation. Vitamin D levels below 30 ng/mL were associated with a higher probability of symptomatic cases.
Dec 2022, Nutrients, https://www.mdpi.com/2072-6643/15/1/169, https://c19p.org/denicolo

24. Alcala-Diaz et al., Calcifediol Treatment and Hospital Mortality Due to COVID-19: A Cohort Study

537 patient vitamin D late treatment study: 81% lower mortality (p=0.04).
Retrospective 537 patients in Spain, 79 treated with calcifediol, showing significantly lower mortality with treatment. The treated group had a higher risk of comorbidity, whereas the control group had lower O2 saturation, higher CURB-65, and higher ARDS (severity measures were included in the multivariate analysis).
May 2021, Nutrients, https://www.mdpi.com/2072-6643/13/6/1760, https://c19p.org/alcaladiaz

25. Sulli et al., Vitamin D and Lung Outcomes in Elderly COVID-19 Patients

130 patient vitamin D prophylaxis study: 76% fewer cases (p=0.0002).
Retrospective 65 elderly COVID-19 patients and 65 matched controls, showing lower vitamin D levels associated with more severe lung involvement, longer disease duration, and higher mortality. Vitamin D supplementation was less common in the COVID-19 group compared to the control group.
Feb 2021, Nutrients, https://www.mdpi.com/2072-6643/13/3/717, https://c19p.org/sulli

26. Burahee et al., Older patients with proximal femur fractures and SARS-CoV-2 infection – An observational study

14 patient vitamin D early treatment study: 93% lower mortality (p=0.01).
Small retrospective study of 29 hip fracture patients in the UK, 14 with COVID-19. All COVID-19 patients were treated with vitamin D except for 2 where testing and supplementation was missed due to a clerical error. The two COVID-19 patients that died were the two that did not receive vitamin D supplementation.
Feb 2021, SICOT-J, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7888253/#!po=1.28205, https://c19p.org/burahee

27. Cangiano et al., Mortality in an Italian nursing home during COVID-19 pandemic: correlation with gender, age, ADL, vitamin D supplementation, and limitations of the diagnostic tests

98 patient vitamin D prophylaxis study: 70% lower mortality (p=0.04).
70% lower mortality with vitamin D supplementation. Analysis of 98 PCR+ nursing home residents in Italy, mean age 90, vitamin D supplementation RR 0.30, p = 0.04. The paper provides the p value for regression but not the effect size. Treatment was 2x per month 25000IU.
Dec 2020, Aging, https://www.aging-us.com/article/202307/text, https://c19p.org/cangianod

28. Ling et al., 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

523 patient vitamin D late treatment study: 80% lower mortality (p=0.001).
80% lower mortality with cholecalciferol booster therapy. Retrospective 986 hospitalized patients in the UK finding that cholecalciferol booster therapy, regardless of baseline serum levels, was associated with a reduced risk of mortality in acute COVID-19 inpatients. Primary cohort of 444 patients, adjusted mortality odds ratio aOR 0.13, p < 0.001. Validation cohort of 541 patients, adjusted mortality odds ratio aOR 0.38, p = 0.018.
Dec 2020, Nutrients, https://www.mdpi.com/2072-6643/12/12/3799, https://c19p.org/ling

29. Annweiler et al., Vitamin D Supplementation Associated to Better Survival in Hospitalized Frail Elderly COVID-19 Patients: The GERIA-COVID Quasi-Experimental Study

61 patient vitamin D prophylaxis study: 93% lower mortality (p=0.02).
Retrospective study finding that regular bolus vitamin D supplementation was associated with less severe COVID-19 and better survival in frail elderly. For those receiving regular supplementation: Adjusted mortality hazard ratio with supplementation HR 0.07, p = 0.017. Risk of severe COVID-19 with supplementation OR 0.08, p = 0.033. For supplementation started after COVID-19 diagnosis: Adjusted mortality hazard ratio HR 0.37, p = 0.28. Risk of severe COVID-19 with supplementation OR 0.46, p = 0.4.
Nov 2020, Nutrients, https://www.mdpi.com/2072-6643/12/11/3377, https://c19p.org/annweiler2

30. Annweiler et al., Vitamin D and survival in COVID-19 patients: A quasi-experimental study

66 patient vitamin D early treatment study: 89% lower mortality (p=0.002).
Vitamin D3 supplementation during or just before COVID-19 was associated with 68% lower mortality and less severe COVID-19 in frail elderly. Retrospective 66 French nursing home residents, mean age 87.7, 9 control patients, and 57 that received an oral bolus of 80,000 IU vitamin D3 either in the week following the suspicion or diagnosis of COVID-19, or during the previous month. 17.5% mortality in the treatment group and 55.6% in the control group.
Oct 2020, The J. Steroid Biochemistry and Molecular Biology, https://www.sciencedirect.com/science/article/pii/S096007602030296X, https://c19p.org/annweiler

31. Salman et al., Role of vitamin-D supplementation in COVID-19 patients

300 patient vitamin D late treatment RCT: 60% lower mortality (p=0.07), 17% lower ventilation (p=0.55), 12% lower ICU admission (p=0.85), and 18% shorter hospitalization (p=0.001).
RCT 300 hospitalized COVID-19 patients in Pakistan receiving either 4,000 IU vitamin D3 supplementation or standard care daily for 14 days. The vitamin D group had significantly faster time to clinical improvement (7 vs 9 days) and shorter length of stay (9 vs 11 days). 65% of patients were vitamin D deficient at baseline.
Jun 2023, Biological and Clinical Sciences Research J., https://bcsrj.com/ojs/index.php/bcsrj/article/view/322, https://c19p.org/salman

32. Mingiano et al., Vitamin D Deficiency in COVID-19 Patients and Role of Calcifediol Supplementation

288 patient vitamin D late treatment study: 39% lower mortality (p=0.04), 23% lower need for oxygen therapy (p=0.22), and 35% shorter hospitalization (p=0.01).
Retrospective 288 hospitalized COVID-19 patients in Italy, showing lower mortality and shorter hospitalization with calcifediol. Results may underestimate the benefits because only higher risk patients with vitamin D deficiency received supplementation. Treated patients also had significantly higher BMI. 83% of patients had vitamin D insufficiency (levels <30 ng/mL). Lower vitamin D levels correlated with higher inflammation markers. Patients with severe vitamin D deficiency (<10 ng/mL) had significantly higher mortality compared to those with levels >10 ng/mL.
Jul 2023, Nutrients, https://www.mdpi.com/2072-6643/15/15/3392, https://c19p.org/mingiano

33. Parant et al., Vitamin D and COVID-19 Severity in Hospitalized Older Patients: Potential Benefit of Prehospital Vitamin D Supplementation

228 patient vitamin D prophylaxis study: 50% lower mortality (p=0.11), 51% lower ICU admission (p=0.008), and 39% lower severe cases (p=0.01).
Retrospective 228 hospitalized COVID-19 patients, median age 78, showing significantly lower risk of ICU admission and severe cases with vitamin D prophylaxis. NCT04877509.
Apr 2022, Nutrients, https://www.mdpi.com/2072-6643/14/8/1641, https://c19p.org/parant

34. Gibbons et al., Association between vitamin D supplementation and COVID-19 infection and mortality

398,996 patient vitamin D prophylaxis PSM study: 33% lower mortality (p<0.0001) and 20% fewer cases (p<0.0001).
PSM retrospective in the USA, showing lower COVID-19 mortality and cases with vitamin D prophylaxis.
Nov 2022, Scientific Reports, https://www.nature.com/articles/s41598-022-24053-4, https://c19p.org/gibbons

35. Tan et al., 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

43 patient vitamin D late treatment study: 80% lower need for oxygen therapy (p=0.04) and 81% lower ICU admission (p=0.07).
Observational study of 43 patients >= 50 years old, with 17 patients receiving vitamin D, magnesium, and vitamin B12 (DMB); and 26 control patients, showing a significantly lower need for oxygen therapy and ICU admission with treatment. DMB OR 0.20 [0.04–0.93] for oxygen therapy and/or intensive care support with multivariate analysis.
Jun 2020, Nutrition, https://www.sciencedirect.com/science/article/pii/S0899900720303002, https://c19p.org/tan

36. Seely et al., Dietary supplements to reduce symptom severity and duration in people with SARS-CoV-2: a double-blind randomised controlled trial

90 patient vitamin D late treatment RCT: 14% improved recovery (p=0.41).
Early terminated low-risk population (no hospitalization) very late treatment (mean 8 days) RCT with 44 patients treated with vitamin C, D, K, and zinc, and 46 control patients, showing no significant differences. Authors acknowledge that the very late treatment is a major limitation, noting that in an ideal setting, "patients would begin taking therapeutic interventions immediately after noticing symptoms". Authors note that patients already had a low symptom burden at baseline and that "it is likely that the majority of the participants had almost fully recovered before starting treatment." Authors note that most participants were young, had few comorbidities and had excellent self-rated health at baseline, leaving less room for improvement. There was low compliance with completing surveys. Data from only 64% of patients was in the main analysis. Authors claim "high internal validity", but the loss of data was statistically significantly..
Sep 2023, BMJ Open, https://bmjopen.bmj.com/lookup/doi/10.1136/bmjopen-2023-073761, https://c19p.org/seelyd

37. Wang et al., Randomized trial of influence of vitamin D on the prevention and improvement of symptomatic COVID-19

202 patient vitamin D prophylaxis RCT: 25% lower progression (p=0.15), 4% fewer cases (p=0.89), and 11% faster viral clearance.
RCT 214 low risk (no hospitalization) healthcare workers in China, showing no significant differences with vitamin D2 prophylaxis using two bolus treatments. Patients with higher vitamin D levels (across both groups) were less likely to be infected. The trial only lasted one month. Two thirds of the cases occurred within the first week, when treatment may have minimal impact on vitamin D levels (calcifediol or calcidiol may be more effective due to delays in conversion). Cases were lower in the intervention group during the last two weeks, after treatment is likely to have increased levels significantly. Regular rather than bolus treatment, longer term treatment, or alternative forms of vitamin D (e.g., calcifediol/calcidiol) may be more effective. Authors report that "4.5% of subjects were lost to follow-up" (1% and 7.6% per group). Figure 2 shows 2 and 0 patients at risk at day 28. This is inconsistent with the reported infection rates and loss to followup, raising..
Mar 2023, Scientific Reports, https://www.nature.com/articles/s41598-024-66267-8, https://c19p.org/wang14

38. Maghbooli et al., 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

106 patient vitamin D late treatment RCT: 40% lower ICU admission (p=0.42) and 17% shorter hospitalization (p=0.1).
RCT 106 hospitalized patients with vitamin D levels <30ng/ml in Iran, 53 treated with calcifediol, showing that treatment was able to correct vitamin D deficiency/insufficiency, resulting in improved immune system function. Hospitalization, ICU duration, ventilation, and mortality was lower with treatment, without reaching statistical significance with the small sample size. The dosage used in this trial was much lower than other trials.
Oct 2021, Endocrine Practice, https://www.sciencedirect.com/science/article/abs/pii/S1530891X21012593, https://c19p.org/maghbooli2

39. Hunt et al., Medications Associated with Lower Mortality in a SARS-CoV-2 Positive Cohort of 26,508 Veterans

26,508 patient vitamin D early treatment study: 47% lower mortality (p=0.0007).
Retrospective 26,508 consecutive COVID+ veterans in the USA, showing lower mortality with multiple treatments including vitamin D. Treatment was defined as drugs administered ≥50% of the time within 2 weeks post-COVID+, and may be a continuation of prophylactic treatment in some cases, and may be early or late treatment in other cases. Further reduction in mortality was seen with combinations of treatments.
Jun 2022, J. General Internal Medicine, https://link.springer.com/10.1007/s11606-022-07701-3, https://c19p.org/hunt

40. Fasano et al., COVID-19 in Parkinson’s Disease Patients Living in Lombardy, Italy

1,486 patient vitamin D prophylaxis study: 42% fewer cases (p=0.05).
Retrospective phone survey of 1,486 Parkinson's disease patients in Italy, showing lower risk of COVID-19 cases with vitamin D supplementation. This paper also presents a case control study of PD patients and family member control patients.
Jun 2021, Movement Disorders, https://movementdisorders.onlinelibrary.wiley.com/doi/10.1002/mds.28176, https://c19p.org/fasano

41. Soliman et al., Impact of Vitamin D Therapy on the Progress COVID-19: Six Weeks Follow-Up Study of Vitamin D Deficient Elderly Diabetes Patients

56 patient vitamin D late treatment RCT: 63% lower mortality (p=0.21), 20% lower ventilation (p=0.56), and 20% improved recovery (p=0.56).
Small RCT with 56 eldery diabetes patients hospitalized in Egypt, 40 treated with cholecalciferol, not showing significant differences.
Aug 2021, Proceedings of Singapore Healthcare, https://journals.sagepub.com/doi/full/10.1177/20101058211041405, https://c19p.org/soliman

42. Ogasawara et al., The effect of 1-hydroxy-vitamin D treatment in hospitalized patients with COVID-19: A retrospective study

312 patient vitamin D late treatment study: 78% lower progression (p=0.05) and 75% lower need for oxygen therapy (p=0.09).
PSM retrospective 312 hospitalized patients in Japan, showing lower progression with vitamin D (alfacalcidol) treatment, statistically significant via KM log-rank.
Aug 2023, Clinical Nutrition, https://www.sciencedirect.com/science/article/pii/S0261561423002790, https://c19p.org/ogasawara

43. Nimer et al., The impact of vitamin and mineral supplements usage prior to COVID-19 infection on disease severity and hospitalization

2,148 patient vitamin D prophylaxis study: 33% lower hospitalization (p=0.001) and 29% lower severe cases (p=0.01).
Retrospective 2,148 COVID-19 recovered patients in Jordan, showing lower risk of severity and hospitalization with vitamin D prophylaxis.
Feb 2022, Bosnian J. Basic Medical Sciences, https://www.bjbms.org/ojs/index.php/bjbms/article/view/7009, https://c19p.org/nimer

44. Hosseini et al., PRevention of COVID-19 with Oral Vitamin D supplemental Therapy in Essential healthCare Teams (PROTECT): Ancillary study of a randomised controlled trial

34 patient vitamin D prophylaxis RCT: 82% fewer cases (p=0.19).
Early terminated prophylaxis RCT for healthcare workers in Canada, showing 0/19 cases with vitamin D prophylaxis vs. 2/15 for control. 100,000IU cholecalciferol at baseline, 10,000IU weekly for 16 weeks.
Jul 2022, Research Square, https://www.researchsquare.com/article/rs-1588325/v1, https://c19p.org/hosseini4

45. Baguma et al., Characteristics of the COVID-19 patients treated at Gulu Regional Referral Hospital, Northern Uganda: A cross-sectional study

481 patient vitamin D late treatment study: 97% lower mortality (p=0.02).
Retrospective COVID+ hospitalized patients in Uganda, 23 patients receiving vitamin D treatment, showing significantly lower mortality with treatment.
Dec 2021, Research Square, https://www.researchsquare.com/article/rs-1193578/v1, https://c19p.org/bagumad

46. Junior et al., Chronic diseases, chest computed tomography, and laboratory tests as predictors of severe respiratory failure and death in elderly Brazilian patients hospitalized with COVID-19: a prospective cohort study

201 patient vitamin D prophylaxis study: 22% lower mortality (p=0.61) and 31% lower progression (p=0.26).
Prospective study of 201 COVID+ hospitalized adults in Brazil, mean age 73, showing a lower risk of mortality and respiratory failure with vitamin D supplementation in unadjusted results, without statistical significance, and a higher risk of progression to mechanical ventilation with vitamin D levels <40ng/dl.
Feb 2022, BMC Geriatrics, https://bmcgeriatr.biomedcentral.com/articles/10.1186/s12877-022-02776-3, https://c19p.org/junior

47. Baykal et al., Correlation of vitamin D level with the clinical-radiological severity of COVID-19 in geriatric patients

75 patient vitamin D late treatment study: 22% lower mortality (p=0.43) and 59% lower ICU admission (p=0.005).
Retrospective 75 patients in Turkey showing lower ICU admission with vitamin D treatment in unadjusted results subject to confounding by time and indication (treatment was given to patients with low levels and only during a certain period). There was no significant difference in outcomes based on vitamin D levels.
May 2022, J. Health Sciences and Medicine, https://dergipark.org.tr/en/doi/10.32322/jhsm.1063405, https://c19p.org/baykal

48. Ma et al., Associations between predicted vitamin D status, vitamin D intake, and risk of SARS-CoV-2 infection and Coronavirus Disease 2019 severity

39,315 patient vitamin D prophylaxis study: 49% lower hospitalization (p=0.04), 7% more symptomatic cases (p=0.25), and 17% fewer cases (p=0.07).
Analysis of 39,915 patients with 1,768 COVID+ cases based on surveys in the Nurses' Health Study II, showing higher predicted vitamin D levels associated with lower risk of COVID-19 cases. There was significantly lower risk of hospitalization with vitamin D supplementation (≥400 IU/d), but no significant differences for cases based on supplementation.
Dec 2021, The American J. Clinical Nutrition, https://academic.oup.com/ajcn/advance-article/doi/10.1093/ajcn/nqab389/6448988, https://c19p.org/ma2

49. Bhat et al., Effect of calcifediol supplementation as add-on therapy on the immune repertoire in recipients of the ChAdOx1 nCoV-19 vaccine: A prospective open-label, placebo-controlled, clinical trial

580 patient vitamin D prophylaxis study: 34% fewer symptomatic cases (p=0.01).
Prospective study of 580 ChAdOx1 recipients, 262 treated with calcifediol (patient choice), showing lower cases with treatment. Supplementation did not significantly affect antibody levels following ChAdOx1 receipt. Calcifediol patients were older (31 vs. 26 in the exposed subgroup containing most patients). 50μg/day calcifediol.
Mar 2023, J. Infection, https://www.sciencedirect.com/science/article/pii/S0163445323001317, https://c19p.org/bhat

50. Sharif et al., Impact of Zinc, Vitamins C and D on Disease Prognosis among Patients with COVID-19 in Bangladesh: A Cross-Sectional Study

vitamin D prophylaxis study: 28% lower severe cases (p=0.001).
Retrospective 962 COVID-19 patients in Bangladesh, showing significantly lower severity with vitamin C, vitamin D, and zinc supplementation, and improved results from the combination of all three.
Nov 2022, Nutrients, https://www.mdpi.com/2072-6643/14/23/5029, https://c19p.org/sharif

51. Said et al., The effect of Nigella sativa and vitamin D3 supplementation on the clinical outcome in COVID-19 patients: A randomized controlled clinical trial

60 patient vitamin D early treatment RCT: 42% improved recovery (p=0.57) and 49% improved viral clearance (p=0.2).
120 patient RCT comparing vitamin D, nigella sativa, and combined vitamin D+nigella sativa, showing improved symptom recovery and viral clearance with both vitamin D and nigella sativa, and further improvements with the combination of both. All patients received vitamin C, zinc, and lactoferrin.
Nov 2022, Frontiers in Pharmacology, https://www.frontiersin.org/articles/10.3389/fphar.2022.1011522/full, https://c19p.org/said

52. Levy et al., Frail Older Adults with Presymptomatic SARS-CoV-2 Infection: Clinical Course and Prognosis

849 patient vitamin D prophylaxis study: 30% lower combined mortality/hospitalization (p=0.05).
Retrospective 849 COVID-19+ patients in skilled nursing homes, showing lower risk of combined hospitalization/death with vitamin D prophylaxis, very close to statistical significance.
Jan 2022, Gerontology, https://www.karger.com/Article/FullText/521412, https://c19p.org/levy

53. Loucera et al., Real world evidence of calcifediol or vitamin D prescription and mortality rate of COVID-19 in a retrospective cohort of hospitalized Andalusian patients

1,604 patient vitamin D prophylaxis PSM study: 33% lower mortality (p=0.009).
Retrospective 15,968 hospitalized patients in Spain showing a significant reduction in mortality associated with the prescription of vitamin D, especially calcifediol, within 15-30 days prior to hospitalization.
Apr 2021, Scientific Reports, https://www.nature.com/articles/s41598-021-02701-5, https://c19p.org/loucera

54. Ma et al., Habitual use of vitamin D supplements and risk of coronavirus disease 2019 (COVID-19) infection: a prospective study in UK Biobank

8,297 patient vitamin D prophylaxis study: 30% fewer cases (p=0.03).
Retrospective 8,297 adults from the UK Biobank showing the habitual use of vitamin D supplements significantly associated with lower risk of COVID-19 cases. Note that the information on vitamin D supplement use was collected a median of 10 years before the COVID-19 tests, so usage may have changed significantly.
Jan 2021, The American J. Clinical Nutrition, https://academic.oup.com/ajcn/advance-article/doi/10.1093/ajcn/nqaa381/6123965, https://c19p.org/ma

55. Jevalikar et al., Lack of association of baseline 25-hydroxyvitamin D levels with disease severity and mortality in Indian patients hospitalized for COVID-19

197 patient vitamin D late treatment study: 82% lower mortality (p=0.12), 34% lower ICU admission (p=0.29), and 32% lower need for oxygen therapy (p=0.06).
Prospective study of 410 hospitalized patients in India showing lower mortality and ICU admission with cholecalciferol treatment, although not statistically significant with the small number of cases. The median total dose was 60,000IU. No significant difference was found for outcomes based on baseline vitamin D deficiency, however this analysis does not appear to account for the deficient patients that were treated with vitamin D.
Dec 2020, Scientific Reports, https://www.nature.com/articles/s41598-021-85809-y, https://c19p.org/jevalikar

56. Sinaci et al., Impact of vitamin D on the course of COVID-19 during pregnancy: A case control study

491 patient vitamin D prophylaxis study: 90% lower severe cases (p=0.35) and 19% more moderate/severe cases (p=0.64).
Retrospective 159 COVID-19+ pregnant women in Turkey and 332 healthy pregnant controls, showing significantly lower vitamin D levels in COVID-19+ patients. 23% of COVID-19 patients where on vitamin D supplementation, while none of the 7 severe cases were on supplementation.
Aug 2021, The J. Steroid Biochemistry and Molecular Biology, https://www.sciencedirect.com/science/article/pii/S0960076021001576, https://c19p.org/sinaci

57. Bagheri et al., Supplement Usage Pattern in a Group of COVID-19 Patients in Tehran

510 patient vitamin D prophylaxis study: 71% lower severe cases (p=0.02) and 38% lower hospitalization (p=0.11).
Retrospective 510 patients in Iran, showing lower risk of severity with vitamin D (statistically significant) and zinc (not statistically significant) supplementation. IR.TUMS.VCR.REC.1398.1063.
Aug 2021, J. Family & Reproductive Health, https://europepmc.org/article/PMC/PMC7868648, https://c19p.org/bagheri

58. Valecha et al., The Effect of Vitamin B12, Magnesium and Vitamin D in COVID-19 among Geriatric Patients

55 patient vitamin D early treatment study: 87% lower ICU admission (p=0.09) and 38% shorter hospitalization (p<0.0001).
Prospective study of 30 patients treated with vitamin D, magnesium, and vitamin B12, and 25 control patients, showing shorter hospitalization and lower oxygen and ICU requirements with treatment. Cholecalciferol 1000IU, magnesium oxide 150mg, vitamin B12 500μg.
Apr 2022, Int. J. Pharmaceutical and Clinical Research, http://impactfactor.org/PDF/IJPCR/14/IJPCR,Vol14,Issue5,Article113.pdf, https://c19p.org/valecha

59. Hafezi et al., Vitamin D enhances type I IFN signaling in COVID-19 patients

80 patient vitamin D ICU study: 63% lower mortality (p=0.04).
Retrospective 80 ICU patients, and in vitro study with human airway epithelial cells, showing that vitamin D enhances host IFN-a/β signaling. Significantly lower mortality was seen with vitamin D treatment.
Oct 2022, Scientific Reports, https://www.nature.com/articles/s41598-022-22307-9, https://c19p.org/hafezi

60. Karimpour-Razkenari et al., Evaluating the Effects of Clinical Characteristics and Therapeutic Regimens on Mortality in Hospitalized Patients with Severe COVID-19

478 patient vitamin D late treatment study: 79% lower mortality (p<0.0001).
Retrospective 478 moderate to severe hospitalized patients in Iran, showing lower mortality with vitamin D treatment.
Oct 2022, J. Pharmaceutical Care, https://publish.kne-publishing.com/index.php/JPC/article/view/10790, https://c19p.org/karimpourrazkenari2

61. Milan et al., Factors Associated with Adverse Outcomes among SARS-CoV-2 Positive Children in a Tertiary Government COVID-19 Referral Hospital in the Philippines

180 patient vitamin D late treatment study: 47% lower mortality (p=0.18), 21% lower ventilation (p=0.53), and 16% lower ICU admission (p=0.69).
Retrospective 180 hospitalized pediatric COVID-19 patients in the Philippines showing lower mortality with vitamin D and zinc, and higher mortality with remdesivir, all without statistical significance. Remdesivir was given to few patients and authors do not provide information on the timing of treatment - confounding by indication may be significant.
Apr 2024, Acta Medica Philippina, https://actamedicaphilippina.upm.edu.ph/index.php/acta/article/view/8392, https://c19p.org/miland

62. Asimi et al., Selenium, zinc, and vitamin D supplementation affect the clinical course of COVID-19 infection in Hashimoto’s thyroiditis

356 patient vitamin D early treatment study: 97% lower ventilation (p<0.0001), 99% lower hospitalization (p<0.0001), and 100% lower severe cases (p<0.0001).
Retrospective 356 Hashimoto's thyroiditis outpatients, 270 taking vitamin D, zinc, and selenium, showing significantly lower hospitalization with treatment. Authors adjust for age, gender, BMI, and smoking status, reporting statistically significant associations with p<0.001 for hospitalization and mechanical ventilation, however they do not report the adjusted risks.
May 2021, Endocrine Abstracts, https://www.endocrine-abstracts.org/ea/0073/ea0073pep14.2, https://c19p.org/asimi

63. Akbar et al., The Association between Lifestyle Factors and COVID-19: Findings from Qatar Biobank

10,000 patient vitamin D prophylaxis study: 19% fewer cases (p=0.02).
Retrospective 10,000 adults in Qatar, showing lower risk of COVID-19 cases with vitamin D supplementation. Authors do not analyze COVID-19 severity.
Nov 2023, Nutrients, https://www.mdpi.com/2072-6643/16/7/1037, https://c19p.org/akbar2

64. van Helmond et al., Vitamin D3 Supplementation at 5000 IU Daily for the Prevention of Influenza-like Illness in Healthcare Workers: A Pragmatic Randomized Clinical Trial

3,082 patient vitamin D prophylaxis study: 98% fewer cases (p=0.07).
Prospective prophylaxis trial with 255 healthcare workers taking vitamin D and 2,827 controls, showing significantly lower influenza-like illness with treatment, and lower COVID-19 cases, without statistical significance. While the intervention and control groups were initially randomized, exclusions were only processed in the treatment arm.
Sep 2022, Nutrients, https://www.mdpi.com/2072-6643/15/1/180, https://c19p.org/vanhelmond

65. Israel et al., Identification of drugs associated with reduced severity of COVID-19: A case-control study in a large population

20,859 patient vitamin D prophylaxis study: 13% lower hospitalization (p=0.003).
Case control study examining medication usage with a healthcare database in Israel, showing lower risk of hospitalization with vitamin D (defined as being picked up within 35 days prior to PCR+). Other patients may have acquired vitamin D supplements outside of the healthcare system.
Jul 2021, Epidemiology and Global Health Microbiology and Infectious Disease, https://elifesciences.org/articles/68165, https://c19p.org/israel2

66. Sainz-Amo et al., COVID-19 in Parkinson’s disease: what holds the key?

211 patient vitamin D prophylaxis study: 33% lower severe cases (p=0.45) and 44% fewer cases (p=0.23).
Case control study with 39 COVID+ and 172 COVID- Parkinson's disease patients in Spain, showing positive and severe cases being less likely to use vitamin D supplementation compared to negative or mild/negative cases respectively. These differences were not statistically significant.
Oct 2020, J. Neurology, https://link.springer.com/article/10.1007/s00415-020-10272-0, https://c19p.org/sainzamo

67. Beigmohammadi et al., 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

60 patient vitamin D ICU RCT: 89% lower mortality (p=0.11), 41% lower hospitalization (p=0.25), and 45% improved recovery (p=0.001).
Small RCT 60 ICU patients in Iran, 30 treated with vitamins A, B, C, D, and E, showing significant improvement in SOFA score and several inflammatory markers at day 7 with treatment. 5,000 IU vitamin A daily, 600,000 IU vitamin D once, 300 IU of vitamin E twice a day, 500 mg vitamin C four times a day, and one ampule daily of B vitamins [thiamine nitrate 3.1 mg, sodium riboflavin phosphate 4.9 mg (corresponding to vitamin B2 3.6 mg), nicotinamide 40 mg, pyridoxine hydrochloride 4.9 mg (corresponding to vitamin B6 4.0 mg), sodium pantothenate 16.5 mg (corresponding to pantothenic acid 15 mg), sodium ascorbate 113 mg (corresponding to vitamin C 100 mg), biotin 60 μg, folic acid 400 μg, and cyanocobalamin 5 μg].
Nov 2021, Trials, https://link.springer.com/article/10.1186/s13063-021-05795-4/fulltext.html, https://c19p.org/beigmohammadi2

68. Efird et al., The Interaction of Vitamin D and Corticosteroids: A Mortality Analysis of 26,508 Veterans Who Tested Positive for SARS-CoV-2

16,338 patient vitamin D early treatment study: 49% lower mortality (p=0.1).
Retrospective 26,508 COVID+ veterans in USA, showing lower mortality with vitamin D use after testing positive (defined as being administered ≥7 days or half of the survival time within 2 weeks after testing), with statistical significance for hospitalized patients.
Dec 2021, Int. J. Environmental Research and Public Health, https://www.mdpi.com/1660-4601/19/1/447/html, https://c19p.org/efird

69. Arroyo-Díaz et al., Previous Vitamin D Supplementation and Morbidity and Mortality Outcomes in People Hospitalised for COVID19: A Cross-Sectional Study

1,267 patient vitamin D prophylaxis study: 12% higher mortality (p=0.59), 43% lower ventilation (p=0.22), 44% lower ICU admission (p=0.03), and 12% shorter hospitalization (p=0.2).
Retrospective 1,267 hospitalized patients in Spain, 189 on vitamin D supplementation before admission, showing lower ICU admission with supplementation, and no statistically significant difference for mortality or ventilation.
Sep 2021, Frontiers in Public Health, https://www.frontiersin.org/articles/10.3389/fpubh.2021.758347/full, https://c19p.org/arroyodiaz

70. Saheb Sharif-Askari et al., Vitamin D modulates systemic inflammation in patients with severe COVID-19

45 patient vitamin D ICU study: 36% shorter ICU admission (p=0.01).
Retrospective 20 ICU patients treated with vitamin D in the UAE, and 25 matched controls, showing significantly shorter ICU stay with treatment. Lower proinflammatory cytokines were associated with lower severity markers. Authors also perform a PBMC In Vitro study, with both the clinical and in vitro studies showing vitamin D attenuated major proinflammatory signaling pathways.
Aug 2022, Life Sciences, https://www.sciencedirect.com/science/article/pii/S0024320522006099, https://c19p.org/sahebsharifaskari

71. Shahid et al., The effects of vitamin D therapy on outcomes for hispanic patients hospitalized for COVID-19

1,478 patient vitamin D late treatment study: 38% lower mortality (p=0.001).
Retrospective 1,478 hospitalized Hispanic patients in the USA with 705 receiving vitamin D treatment, showing lower mortality with treatment in unadjusted results. Very minimal information is currently available.
Jun 2022, Abstracts from the 2022 Annual Meeting of the Society of General Internal Medicine, J. General Internal Medicine, https://link.springer.com/10.1007/s11606-022-07653-8, https://c19p.org/shahid

72. Khan et al., Oral Co-Supplementation of Curcumin, Quercetin, and Vitamin D3 as an Adjuvant Therapy for Mild to Moderate Symptoms of COVID-19—Results From a Pilot Open-Label, Randomized Controlled Trial

50 patient vitamin D early treatment RCT: 33% improved recovery (p=0.15) and 50% improved viral clearance (p=0.009).
RCT 50 COVID+ outpatients in Pakistan, 25 treated with curcumin, quercetin, and vitamin D, showing significantly faster viral clearance, significantly improved CRP, and faster resolution of acute symptoms (p=0.154). 168mg curcumin, 260mg quercetin and 360IU cholecalciferol.
Apr 2022, Frontiers in Pharmacology, https://www.frontiersin.org/articles/10.3389/fphar.2022.898062/full, https://c19p.org/khan4

73. Domazet Bugarin et al., Vitamin D Supplementation and Clinical Outcomes in Severe COVID-19 Patients—Randomized Controlled Trial

152 patient vitamin D ICU RCT: 21% lower mortality (p=0.2), no change in recovery (p=0.71), and 6% longer hospitalization (p=0.76).
Very late stage RCT 155 ICU patients in Croatia with low vitamin D levels, showing no significant differences with 10,000IU cholecalciferol daily. Calcifediol or calcitriol, which avoids several days delay in conversion, may be more successful, especially with this very late stage usage. The baseline mean age and median WHO scores for the treatment and control groups are both higher than the respective values reported for all patients combined, which is not possible. The trial was registered after completion in May 2022.
Feb 2023, Nutrients, https://www.mdpi.com/2072-6643/15/5/1234, https://c19p.org/domazetbugarin

74. Subramanian et al., Vitamin D, D-binding protein, free vitamin D and COVID-19 mortality in hospitalized patients

467 patient vitamin D prophylaxis study: 27% lower mortality (p=0.12).
Retrospective 427 hospitalized COVID-19 patients in the United Kingdom, showing lower mortality with vitamin D supplementation (p=0.12), and higher mortality with both low and high vitamin D levels compared to a reference range of 50-74 nmol/L.
Jan 2022, The American J. Clinical Nutrition, https://academic.oup.com/ajcn/advance-article/doi/10.1093/ajcn/nqac027/6518440, https://c19p.org/subramanian

75. Regalia et al., Vitamin D Status and SARS-CoV-2 Infection in a Cohort of Kidney Transplanted Patients

179 patient vitamin D prophylaxis study: 33% fewer cases (p=0.21).
Retrospective 61 COVID+ kidney transplant patients and 122 matched controls, showing significantly lower vitamin D levels in COVID+ patients, and lower cases with vitamin D supplementation, without statistical significance.
Jan 2022, Nutrients, https://www.mdpi.com/2072-6643/14/2/317/htm, https://c19p.org/regalia

76. Dudley et al., Revisiting vitamin D status and supplementation for in-patients with intellectual and developmental disability in the North of England, UK

64 patient vitamin D prophylaxis study: 22% fewer symptomatic cases (p=0.65).
Retrospective 64 patients with intellectual and developmental disability in the UK, showing no significant difference in COVID-19 status with vitamin D supplementation. Only 6 patients were not on vitamin D supplementation.
May 2021, BJPsych Bulletin, https://www.cambridge.org/core/journals/bjpsych-bulletin/article/revisiting-vitamin-d-status-and-supplementation-for-inpatients-with-intellectual-and-developmental-disability-in-the-north-of-england-uk/9ABB85B839DD2343107CCD98B10A81EA, https://c19p.org/dudley

77. Levitus et al., The Effect of Vitamin D Supplementation on Severe COVID-19 Outcomes in Patients With Vitamin D Insufficiency

129 patient vitamin D prophylaxis study: 31% lower severe cases (p=0.25).
Retrospective 129 hospitalized patients with vitamin D levels measured within 90 days prior to admission, showing lower, but not statistically significant, risk of severe cases with vitamin D supplementation among patients with levels <20ng/mL or <12ng/mL. For <30ng/mL, lower (but not statistically significant) risk was seen overall but not for ≥50,000IU (the sample size is not given, it may be extremely small for this case). Only minimal details for <30ng/mL are provided, and no details for <20ng/mL or <12ng/mL are provided. The potential effect of supplementation on the risk of a case severe enough for hospitalization is not included.
May 2021, J. the Endocrine Society, https://academic.oup.com/jes/article/5/Supplement_1/A279/6240740, https://c19p.org/levitus

78. Giannini et al., Effectiveness of In-Hospital Cholecalciferol Use on Clinical Outcomes in Comorbid COVID-19 Patients: A Hypothesis-Generating Study

91 patient vitamin D late treatment study: 37% lower combined mortality/ICU admission (p=0.13).
Retrospective 91 hospitalized patients, 36 treated with high-dose cholecalciferol, showing lower combined death/ICU admission with treatment. Authors also analyze the relationship with comorbidity burden, finding that the positive effect of high-dose cholecalciferol on the combined endpoint was significantly amplified with increasing comorbidity burden.
Jan 2021, Nutrients , https://www.mdpi.com/2072-6643/13/1/219/htm, https://c19p.org/giannini

79. Arboleda et al., EAST framework to promote adherence to nutritional supplementation: a strategy to mitigate COVID-19 within health workers

823 patient vitamin D prophylaxis study: 36% fewer cases (p=0.03).
Prospective study of 1,063 health workers in Colombia showing lower COVID-19 infection rates with adherence to a vitamin D and C supplementation plan, however very limited baseline information is provided for the adherent vs. non-adherent groups, and no adjusted results are provided. Higher risk patients had a much higher adherence rate, suggesting that the efficacy of treatment may be significantly higher than observed.
Mar 2024, Behavioural Public Policy, https://www.cambridge.org/core/product/identifier/S2398063X24000113/type/journal_article, https://c19p.org/arboleda

80. Vasheghani et al., The relationship between serum 25-hydroxyvitamin D levels and the severity of COVID-19 disease and its mortality

508 patient vitamin D prophylaxis study: 30% lower mortality (p=0.45) and 64% lower ICU admission (p=0.009).
Retrospective 508 hospitalized COVID-19 patients in Iran showing lower mortality with vitamin D supplementation (not reaching statistical significance), and an association between lower vitamin D levels and disease severity, ICU admission, and increased mortality. Details of supplementation are not provided. The multivariate result for vitamin D deficiency is in the preprint, the journal version only contains the multivariate result for serum level.
Jan 2021, Scientific Reports, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8413335/, https://c19p.org/vasheghani

81. Din Ujjan et al., The possible therapeutic role of curcumin and quercetin in the early-stage of COVID-19—Results from a pragmatic randomized clinical trial

50 patient vitamin D early treatment RCT: 29% improved recovery (p=0.11) and 91% improved viral clearance (p=0.05).
Small RCT with 50 outpatients, 25 treated with curcumin, quercetin, and vitamin D, showing improved recovery and viral clearance with treatment. 168mg curcumin, 260mg, 360IU vitamin D3 daily for 14 days.
Jan 2023, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2022.1023997/full, https://c19p.org/dinujjan

82. Hafez et al., Factors Influencing Disease Stability and Response to Tocilizumab Therapy in Severe COVID-19: A Retrospective Cohort Study

42 patient vitamin D late treatment study: 94% lower mortality (p=0.07).
Retrospective 49 severe COVID-19 patients treated with tocilizumab, showing lower mortality with vitamin D treatment and a dose-dependent response.
Aug 2022, Antibiotics, https://www.mdpi.com/2079-6382/11/8/1078, https://c19p.org/hafez2

83. Jabeen et al., Protective Effect of Vitamin-D Supplementation in Patients of Acute Coronary Syndrome During COVID-19 Pandemic

40 patient vitamin D prophylaxis study: 89% fewer symptomatic cases (p=0.11).
Prospective study of 40 acute coronary syndrome patients in Pakistan, 20 given a single dose of 200,000IU vitamin D, showing lower incidence of COVID-19 in the following 2 months.
May 2022, Pakistan J. Medical and Health Sciences, https://pjmhsonline.com/index.php/pjmhs/article/view/773, https://c19p.org/jabeen

84. Louca et al., Modest effects of dietary supplements during the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom Study app

372,720 patient vitamin D prophylaxis study: 8% fewer cases (p=0.0007).
Survey analysis of dietary supplements showing vitamin D usage associated with lower incidence of COVID-19. These results are for PCR+ cases only, they do not reflect potential benefits for reducing the severity of cases. A number of biases could affect the results, for example users of the app may not be representative of the general population, and people experiencing symptoms may be more likely to install and use the app.
Nov 2020, BMJ Nutrition, Prevention & Health, https://nutrition.bmj.com/content/4/1/149, https://c19p.org/louca

85. Shehab et al., Immune-boosting effect of natural remedies and supplements on progress of, and recovery from COVID-19 infection

253 patient vitamin D prophylaxis study: 46% lower severe cases (p=0.2).
Retrospective survey-based analysis of 349 COVID-19 patients, showing a lower risk of severe cases with vitamin D, zinc, turmeric, and honey prophylaxis in unadjusted analysis, without statistical significance. REC/UG/2020/03.
Feb 2022, Tropical J. Pharmaceutical Research, https://www.tjpr.org/admin/12389900798187/2022_21_2_14.pdf, https://c19p.org/shehab

86. Tylicki et al., Predictors of Mortality in Hemodialyzed Patients after SARS-CoV-2 Infection

133 patient vitamin D prophylaxis study: 14% lower mortality (p=0.61).
Retrospective 133 COVID+ hemodialysis patients in Poland, showing lower mortality with existing vitamin D use, without statistical significance.
Jan 2022, J. Clinical Medicine, https://www.mdpi.com/2077-0383/11/2/285, https://c19p.org/tylicki

87. Mazziotti et al., Vitamin D deficiency, secondary hyperparathyroidism and respiratory insufficiency in hospitalized patients with COVID-19

348 patient vitamin D late treatment study: 19% lower mortality (p=0.49) and 67% higher ventilation (p=0.08).
Retrospective 348 hospitalized patients in Italy showing vitamin D deficiency associated with acute hypoxemic respiratory failure. Vitamin D supplementation during hospitalization was not significantly associated with mortality or ventilation.
Mar 2021, J. Endocrinological Investigation, https://link.springer.com/article/10.1007/s40618-021-01535-2, https://c19p.org/mazziotti

88. Bychinin et al., Effect of vitamin D3 supplementation on cellular immunity and inflammatory markers in COVID-19 patients admitted to the ICU

106 patient vitamin D ICU RCT: 27% lower mortality (p=0.18), 7% lower ventilation (p=0.68), 94% longer ICU admission (p=0.001), and 41% longer hospitalization (p=0.007).
RCT ICU patients in Russia, showing significantly increased lymphocyte counts with treatment. Mortality was lower but without statistical significance. 40% of patients were on mechanical ventilation at baseline in the treatment group, compared to 30% in the placebo group. Authors state that there has been 6 RCTs for COVID-19 and vitamin D, however there was at least 23 at the time of publication: [c19early.org].
Nov 2022, Scientific Reports, https://www.nature.com/articles/s41598-022-22045-y, https://c19p.org/bychinin2

89. Murai et al., 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

237 patient vitamin D late treatment RCT: 49% higher mortality (p=0.43), 48% lower ventilation (p=0.09), 25% lower ICU admission (p=0.3), and 7% higher hospital discharge (p=0.63).
Very late stage (mean 10 days from symptom onset, 90% on oxygen at baseline) vitamin D supplementation RCT not showing significant differences. Ethnicity was poorly matched between arms, and diabetes was 41% in the treatment arm vs. 29% in the control arm. Baseline ventilation was 15% in the treatment arm vs. 12% control. Calcifediol or calcitriol, which avoids several days delay in conversion, may be more successful, especially with this very late stage usage. Treatment was dissolved in 10mL of peanut oil.
Nov 2020, JAMA, https://jamanetwork.com/journals/jama/fullarticle/2776738, https://c19p.org/murai

90. Aweimer et al., Mortality rates of severe COVID-19-related respiratory failure with and without extracorporeal membrane oxygenation in the Middle Ruhr Region of Germany

149 patient vitamin D ICU study: 21% lower mortality (p=0.31).
Retrospective 149 patients under invasive mechanical ventilation in Germany showing no significant difference in mortality with vitamin D prophylaxis in unadjusted results.
Mar 2023, Scientific Reports, https://www.nature.com/articles/s41598-023-31944-7, https://c19p.org/aweimer

91. Güven et al., 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

175 patient vitamin D ICU study: 25% lower mortality (p=0.32).
Retrospective 175 ICU patients, 113 treated with a single dose of 300,000IU intramuscular cholecalciferol, showing lower mortality with treatment, but not reaching statistical significance. Calcifediol or calcitriol, which avoids several days delay in conversion, may be more successful, especially with this very late stage usage.
Jul 2021, European J. Clinical Nutrition, https://www.nature.com/articles/s41430-021-00984-5, https://c19p.org/guven

92. Elhadi et al., Epidemiology, outcomes, and utilization of intensive care unit resources for critically ill COVID-19 patients in Libya: A prospective multi-center cohort study

465 patient vitamin D ICU study: 23% lower mortality (p=0.29).
Prospective study of 465 COVID-19 ICU patients in Libya showing no significant differences with treatment.
Apr 2021, PLOS ONE, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251085, https://c19p.org/elhadi

93. Ahmed et al., Causal Inference and COVID-19 Nursing Home Patients: Identifying Factors That Reduced Mortality Risk

vitamin D prophylaxis study: 10% lower mortality (p=0.28).
Retrospective causal inference analysis of 4,091 COVID+ long-term care high risk patients in the USA, showing lower mortality with vitamin D, without statistical significance.
Nov 2021, medRxiv, https://www.medrxiv.org/content/10.1101/2021.11.18.21266489, https://c19p.org/ahmed3

94. Shamsi et al., Survival and Mortality in Hospitalized Children with COVID-19: A Referral Center Experience in Yazd, Iran

183 patient vitamin D late treatment study: 58% lower mortality (p=0.7).
Retrospective 183 hospitalized pediatric COVID-19 patients in Iran, showing no significant difference in mortality with in unadjusted results.
Jul 2023, Canadian J. Infectious Diseases and Medical Microbiology, https://www.hindawi.com/journals/cjidmm/2023/5205188/, https://c19p.org/shamsid

95. Abdulateef et al., COVID-19 severity in relation to sociodemographics and vitamin D use

427 patient vitamin D prophylaxis study: 41% lower hospitalization (p=0.3).
Survey of 428 recovered COVID-19 patients in Iraq, showing fewer hospital visits for patients on prophylactic vitamin C or D. Hospitalization was lower for those on vitamin C, D, or zinc, without statistical significance.
Apr 2021, Open Medicine, https://www.degruyter.com/document/doi/10.1515/med-2021-0273/html, https://c19p.org/abdulateef

96. Blanch-Rubió et al., Influence of anti-osteoporosis treatments on the incidence of COVID-19 in patients with non-inflammatory rheumatic conditions

2,102 patient vitamin D prophylaxis study: 8% fewer cases (p=0.68).
Retrospective 2,102 rheumatology patients in Spain showing no significant difference in cases with vitamin D supplementation. Details of vitamin D supplementation are not providied - other patients may have also independently taken vitamin D.
Oct 2020, Aging, https://www.aging-us.com/article/104117/text, https://c19p.org/blanchrubio

97. Krishnan et al., Clinical comorbidities, characteristics, and outcomes of mechanically ventilated patients in the State of Michigan with SARS-CoV-2 pneumonia

152 patient vitamin D late treatment study: 19% lower mortality (p=0.42).
Retrospective 152 mechanically ventilated patients in the USA showing unadjusted lower mortality with vitamin C, vitamin D, HCQ, and zinc treatment, statistically significant only for vitamin C.
Jul 2020, J. Clinical Anesthesia, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7369577/, https://c19p.org/krishnand

98. Guldemir et al., Clinical characteristics of bus drivers and field officers infected with COVID-19: A cross-sectional study from Istanbul

477 patient vitamin D prophylaxis study: 5% lower hospitalization (p=0.89).
Retrospective 477 COVID+ public transportation workers in Turkey, showing no significant difference in hospitalization with vitamin D use in unadjusted results.
Nov 2022, Work, https://www.medra.org/servlet/aliasResolver?alias=iospress&doi=10.3233/WOR-220292, https://c19p.org/guldemird

99. Mahmood et al., Coronavirus in HIP Fractures CHIP 2: Is Vitamin D Deficiency Associated with Increased Mortality from COVID-19 Infections in A Hip Fracture Population?

490 patient vitamin D prophylaxis study: 9% lower mortality (p=0.67).
Retrospective 517 hip fracture patients in the UK with vitamin D levels measured during COVID-19 admission, not showing significant differences in mortality for supplementation in unadjusted analysis with no group details and subject to confounding by indication. There was also no significant effect based on deficiency.
Dec 2021, European J. Medical and Health Sciences, https://ej-med.org/index.php/ejmed/article/view/1159, https://c19p.org/mahmood

100. Mohseni et al., Do body mass index (BMI) and history of nutritional supplementation play a role in the severity of COVID-19? A retrospective study

603 patient vitamin D prophylaxis study: 12% fewer cases (p=0.09).
Retrospective 603 patients in Iran, 192 taking vitamin D supplements, showing no significant difference in COVID-19 cases in unadjusted results. IR.SHOUSHTAR.REC.1399.015.
Aug 2021, Nutrition & Food Science, https://www.emerald.com/insight/content/doi/10.1108/NFS-11-2020-0421/full/html, https://c19p.org/mohseni

101. Holt et al., Risk factors for developing COVID-19: a population-based longitudinal study (COVIDENCE UK)

15,227 patient vitamin D prophylaxis study: 7% fewer cases (p=0.53).
Prospective survey-based study with 15,227 people in the UK, showing lower risk of COVID-19 cases with vitamin A, vitamin D, zinc, selenium, probiotics, and inhaled corticosteroids; and higher risk with metformin and vitamin C. Statistical significance was not reached for any of these. Except for vitamin D, the results for treatments we follow were only adjusted for age, sex, duration of participation, and test frequency.
Mar 2021, Thorax, https://thorax.bmj.com/content/early/2021/11/02/thoraxjnl-2021-217487, https://c19p.org/holtd

102. Lázaro et al., Vitamin D deficit in type 2 diabetes patients during COVID-19 lockdown with and without supplementation

239 patient vitamin D prophylaxis study: 27% fewer cases (p=1).
Analysis of 239 consecutive diabetic patients, 97 taking vitamin D supplements, showing significantly higher vitamin D levels in supplemented patients. There was no statistically significant difference in cases based on supplementation, with only 3 cases total.
Sep 2021, Endocrine Abstracts, https://www.endocrine-abstracts.org/ea/0070/ea0070ep552, https://c19p.org/lazaro

103. Zangeneh et al., Survival analysis based on body mass index in patients with Covid-19 admitted to the intensive care unit of Amir Al-Momenin Hospital in Arak – 2021

vitamin D ICU study: 26% higher mortality (p=0.4).
Retrospective 193 ICU patients in Iran, showing no significant difference with vitamin D treatment.
May 2022, Obesity Medicine, https://www.sciencedirect.com/science/article/pii/S245184762200032Xhttps://www.sciencedirect.com/science/article/pii/S245184762200032X/pdf, https://c19p.org/zangenehd

104. Cannata-Andía et al., A single-oral bolus of 100,000 IU of cholecalciferol at hospital admission did not improve outcomes in the COVID-19 disease: the COVID-VIT-D — a randomised multicentre international clinical trial

543 patient vitamin D late treatment RCT: 44% higher mortality (p=0.31), 5% higher ICU admission (p=0.82), and 5% longer hospitalization.
RCT 274 very late stage (>80% pulmonary involvement at baseline) hospitalized COVID-19 patients treated with a single dose of cholecalciferol, and 269 control patients, showing no significant differences. High serum calcidiol levels at admission were associated with lower pulmonary involvement, shorter hospitalization, and lower ICU admission. Serum levels increased in the treatment group, however average levels were still insufficient at discharge. Calcifediol or calcitriol, which avoids several days delay in conversion, may be more successful, especially with this very late stage usage. 100,000IU cholecalciferol.
Feb 2022, BMC Medicine, https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-022-02290-8, https://c19p.org/cannataandia

105. Golabi et al., 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

106 patient vitamin D prophylaxis study: 25% more cases (p=0.56).
Analysis of vitamin D and zinc levels in 53 PCR+ outpatients and 53 matched controls, showing lower zinc levels in COVID-19 patients, and increased risk of cases and symptoms with vitamin D deficiency. There was no significant difference in the use of supplements between cases and controls. IR.ABADANUMS.REC.1399.073.
Aug 2021, Nutrients, https://www.mdpi.com/2072-6643/13/10/3368, https://c19p.org/golabi2

106. Fairfield et al., Association of Vitamin D Prescribing and Clinical Outcomes in Adults Hospitalized with COVID-19

158,835 patient vitamin D late treatment study: 9% higher mortality (p<0.0001) and 41% higher ventilation (p<0.0001).
N3C retrospective showing higher risk with vitamin D treatment for hospitalized patients. As noted by authors, confounding by indication may be significant. The more extreme ventilation result, which is a significant outlier among all studies, is consistent with such confounding. Timing, dose, and duration of treatment were not used.
Jul 2022, Nutrients, https://www.mdpi.com/2072-6643/14/15/3073, https://c19p.org/fairfield

107. Oristrell et al., Vitamin D supplementation and COVID-19 risk: a population-based, cohort study

404,109 patient vitamin D prophylaxis study: 1% higher mortality (p=0.91) and 1% fewer cases (p=0.65).
Retrospective study of cholecalciferol and calcitriol supplementation in Catalonia showing a small but significant lower risk of cases with cholecalciferol, but no significant difference for mortality, or for calcitriol supplementation. Significant benefit was found for cases, severity, and mortality in patients achieving serum vitamin D levels ≥30ng/ml.
Jul 2021, J. Endocrinological Investigation, https://link.springer.com/article/10.1007/s40618-021-01639-9, https://c19p.org/oristrell2

108. Al Sulaiman et al., Survival implications vs. complications: unraveling the impact of vitamin D adjunctive use in critically ill patients with COVID-19—A multicenter cohort study

288 patient vitamin D ICU study: 22% higher mortality (p=0.25), 27% higher ventilation (p=0.05), 17% higher ICU admission (p=0.07), and no change in hospitalization (p=1).
Retrospective 1,435 ICU patients in Saudi Arabia, showing no significant difference in mortality, and longer mechanical ventilation with treatment. Vitamin D patients had higher Q1, median, and Q3 SOFA scores after propensity score matching. 98% of patients were treated with cholecalciferol.
Aug 2023, Frontiers in Medicine, https://www.frontiersin.org/articles/10.3389/fmed.2023.1237903/full, https://c19p.org/alsulaiman5

109. Aldwihi et al., Patients’ Behavior Regarding Dietary or Herbal Supplements before and during COVID-19 in Saudi Arabia

738 patient vitamin D prophylaxis study: 49% higher hospitalization (p=0.002).
Retrospective survey-based analysis of 738 COVID-19 patients in Saudi Arabia, showing lower hospitalization with vitamin C, turmeric, zinc, and nigella sativa, and higher hospitalization with vitamin D. For vitamin D, most patients continued prophylactic use. For vitamin C, the majority of patients continued prophylactic use. For nigella sativa, the majority of patients started use during infection. Authors do not specify the fraction of prophylactic use for turmeric and zinc.
May 2021, Int. J. Environmental Research and Public Health, https://www.mdpi.com/1660-4601/18/10/5086, https://c19p.org/aldwihid

110. Ullah et al., COVID-19 in patients with hepatobiliary and pancreatic diseases in East London: a single-centre cohort study

14,849 patient vitamin D prophylaxis study: 42% higher mortality (p=0.35) and 146% more cases (p<0.0001).
Retrospective 15,440 patients with hepatobiliary and pancreatic diseases in the United Kingdom, 226 with confirmed COVID-19, showing higher risk with vitamin D supplementation. Results are likely confounded by impaired vitamin D processing and propensity to prescribe supplementation based on specifics of each patient's disease and vitamin D levels. Adjustments used broad age ranges, likely adding to residual confounding.
Mar 2021, Pancreatology, https://www.sciencedirect.com/science/article/abs/pii/S1424390320307298, https://c19p.org/ullah2

111. Assiri et al., COVID-19 related treatment and outcomes among COVID-19 ICU patients: A retrospective cohort study

118 patient vitamin D ICU study: 66% higher mortality (p=0.6).
Retrospective 118 ICU patients in Saudi Arabia showing no significant differences in unadjusted results with zinc, vitamin D, and favipiravir treatment.
Aug 2021, J. Infection and Public Health, https://www.sciencedirect.com/science/article/pii/S1876034121002495, https://c19p.org/assiri

112. Brunvoll et al., Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial

34,601 patient vitamin D prophylaxis RCT: 11% lower hospitalization (p=1), 20% higher severe cases (p=0.17), and no change in cases (p=0.98).
RCT 17,278 low-risk patients (zero mortality) treated with 5mL/day cod liver oil (~400IU vitamin D) and 17,323 placebo patients in Norway with, showing no significant differences with treatment. The placebo group had higher vitamin D at baseline, and both groups had comparable vitamin D during treatment (74 vs. 63 nmol/L). 23% of control patients took vitamin D supplements and 62% consumed fatty fish (typically a good source of vitamin D). Adherence was low (<70% for "strict" compliance, which only required >0.5L consumed, or treatment for > "2-3" months).
Sep 2022, BMJ, https://www.bmj.com/lookup/doi/10.1136/bmj-2022-071245, https://c19p.org/brunvoll

113. Mariani et al., High-dose vitamin D versus placebo to prevent complications in COVID-19 patients: Multicentre randomized controlled clinical trial

218 patient vitamin D late treatment RCT: 25% lower ventilation (p=0.85), 27% lower ICU admission (p=0.62), and 3% lower progression (p=0.82).
Late stage RCT with 115 patients treated with a single dose of 500,000IU cholecalciferol and 103 placebo patients, showing no significant differences. Authors do not explain why they did very late treatment with cholecalciferol instead of calcifediol or calcitriol, which would avoid several days delay in conversion. Baseline vitamin D levels were relatively high, limiting the potential benefit.
May 2022, PLOS ONE, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0267918https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0267918&type=printable, https://c19p.org/mariani

114. Cereda et al., Vitamin D supplementation and outcomes in coronavirus disease 2019 (COVID-19) patients from the outbreak area of Lombardy, Italy

197 patient vitamin D prophylaxis study: 73% higher mortality (p=0.14) and 17% higher hospitalization (p=0.68).
Retrospective 105 Parkinson's disease patients, 92 caregivers, and 127 hospital inpatients, showing higher, but not statistically significant mortality and hospitalization with treatment. Supplementation was defined as >=25,000IU/month for at least 3 months.
Nov 2020, Nutrition, https://www.sciencedirect.com/science/article/pii/S0899900720303385, https://c19p.org/cereda2

115. Pecina et al., Vitamin D Status and Severe COVID-19 Disease Outcomes in Hospitalized Patients

92 patient vitamin D prophylaxis study: 70% higher mortality (p=0.52), 10% higher ventilation (p=0.89), and 30% higher ICU admission (p=0.61).
Retrospective 92 hospitalized patients not showing significant differences in outcomes based on vitamin D status or supplementation.
Aug 2021, J. Primary Care & Community Health , https://journals.sagepub.com/doi/full/10.1177/21501327211041206, https://c19p.org/pecina

116. Jolliffe et al., Effect of a test-and-treat approach to vitamin D supplementation on risk of all cause acute respiratory tract infection and covid-19: phase 3 randomised controlled trial (CORONAVIT)

4,464 patient vitamin D prophylaxis RCT: 41% higher hospitalization (p=0.16) and 9% more cases (p=0.55).
RCT 5,979 low risk patients (0 COVID-19 deaths) in the UK, showing no significant differences with vitamin D prophylaxis. CORONAVIT. NCT04579640. For more discussion see 1 , 2 . 51% of confirmed COVID-19 cases were hospitalized in the control arm which is 7 times the median rate in other studies reporting both cases and hospitalization as of Sep 2022 (7.2%), suggesting possible issues with the data or major differences between the study population and the general population. Authors do not provide exact start/end dates (month only) or specify when infections occurred, however based on cases in the UK, most infections may have been closer to the start of the trial when vitamin D levels may still have been relatively low. Reportedly, authors do not plan to analyze this issue, and have declined to allow one of the funders access to the data. 3 present an RCT showing conflicting results, 78% lower cases with vitamin D prophylaxis. In comparison, 3 used a higher dose, the participants had..
Mar 2022, BMJ, https://www.bmj.com/lookup/doi/10.1136/bmj-2022-071230, https://c19p.org/jolliffe2

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