COVID-19 drug repurposing research Wikipedia
During the COVID-19 pandemic, there has been interest in vitamin D status and supplements, given the significant overlap in the risk factors for severe COVID-19 and vitamin D deficiency. These include obesity, older age, and Black or Asian ethnic origin, and it is notable that vitamin D deficiency is particularly common within these groups.
The National Institutes of Health (NIH) COVID-19 Treatment Guidelines stated in July 2020 that "there are insufficient data to recommend either for or against the use of vitamin D for the prevention or treatment of COVID-19."
The general recommendation to consider taking vitamin D supplements, particularly given the levels of vitamin D deficiency in Western populations, has been repeated. As of February 2021, the English National Institute for Health and Care Excellence (NICE) continued to recommend small doses of supplementary vitamin D for people with little exposure to sunshine, but recommended that practitioners should not offer a vitamin D supplement solely to prevent or treat COVID-19, except as part of a clinical trial.
Multiple studies have reported links between pre-existing vitamin D deficiency and the severity of the disease. Several systematic reviews and meta-analyses of these show that vitamin D deficiency may be associated with a higher probability of becoming infected with COVID-19, and have clearly demonstrated there are significant associations between deficiency and a greater severity of the disease, including relative increases in hospitalization and mortality rates of about 80%.   The quality of some of the studies included and whether this demonstrates a causal relationship has been questioned.
Many clinical trials are underway or have been completed assessing the use of oral vitamin D and its metabolites such as calcifediol for prevention or treatment of COVID-19 infection, especially in people with vitamin D deficiency.   
The effects of oral vitamin D supplementation on the need for intensive care unit (ICU) admission and mortality in hospitalized COVID-19 patients has been the subject of a meta-analysis. A much lower ICU admission rate was found in patients who received vitamin D supplementation, which was only 36% of that seen in patients without supplementation (p<0.0001). No significant effects on mortality were found in this meta-analysis. The certainty of these analyses is limited by the heterogenicity in the studies which include both vitamin D3 (cholecalciferol) and calcifediol, but these findings indicate a potential role in improving COVID-19 severity, with more robust data being required to substantiate any effects on mortality. 
Calcifediol, which is 25-hydroxyvitamin D, is more quickly activated,200 and has been used in several trials. Review of the published results suggests that calcifediol supplementation may have a protective effect on the risk of ICU admissions in COVID-19 patients.
- 188) Martineau AR, Forouhi NG (September 2020). "Vitamin D for COVID-19: a case to answer?". The Lancet. Diabetes & Endocrinology. 8 (9): 735–6. doi:10.1016/S2213-8587(20)30268-0. PMC 7398646. PMID 32758429.
- 189) "Vitamin D". Coronavirus Disease 2019 (COVID-19) Treatment Guidelines. National Institutes of Health (NIH). 17 July 2020. Retrieved 22 February 2021. ‹See TfM›Public Domain This article incorporates text from this source, which is in the public domain.
- 190) COVID-19 rapid guideline: vitamin D (PDF) (Technical report). National Institute for Health and Care Excellence (NICE). December 2020. ISBN 978-1-4731-3942-8. NG187. Retrieved 22 February 2021.
- Damascena, Alialdo Dantas; Azevedo, Laylla Mirella Galvão; Oliveira, Tarcio de Almeida; Santana, Jerusa da Mota; Pereira, Marcos (12 August 2021). "Addendum to vitamin D deficiency aggravates COVID-19: systematic review and meta-analysis". Critical Reviews in Food Science and Nutrition: 1–6. doi:10.1080/10408398.2021.1951652. ISSN 1549-7852. PMID 34384300. S2CID 236997712.
- Kazemi A, Mohammadi V, Aghababaee SK, Golzarand M, Clark CC, Babajafari S (March 2021). "Association of Vitamin D Status with SARS-CoV-2 Infection or COVID-19 Severity: A Systematic Review and Meta-analysis". Advances in Nutrition. doi:10.1093/advances/nmab012. PMC 7989595. PMID 33751020.
- Petrelli F, Luciani A, Perego G, Dognini G, Colombelli PL, Ghidini A (March 2021). "Therapeutic and prognostic role of vitamin D for COVID-19 infection: A systematic review and meta-analysis of 43 observational studies". The Journal of Steroid Biochemistry and Molecular Biology. 211: 105883. doi:10.1016/j.jsbmb.2021.105883. PMC 7997262. PMID 33775818.
- Bassatne A, Basbous M, Chakhtoura M, Zein OE, Rahme M, Fuleihan GE (March 2021). "The link between COVID-19 and Vitamin D (VIVID): a systematic review and meta-analysis". Metabolism (Systematic review). 119: 154753. doi:10.1016/j.metabol.2021.154753. PMC 7989070. PMID 33774074.
- Evidence reviews for the use of vitamin D supplementation as prevention and treatment of COVID-19 (PDF) (Report). National Institute for Health and Care Excellence (NICE). December 2020.
- "International clinical trials assessing vitamin D in people with COVID-19". ClinicalTrials.gov. Retrieved 11 June 2021.
- Quesada-Gomez JM, Entrenas-Castillo M, Bouillon R (September 2020). "Vitamin D receptor stimulation to reduce acute respiratory distress syndrome (ARDS) in patients with coronavirus SARS-CoV-2 infections: Revised Ms SBMB 2020_166". The Journal of Steroid Biochemistry and Molecular Biology. 202: 105719. doi:10.1016/j.jsbmb.2020.105719. PMC 7289092. PMID 32535032.
- I Shah K, Saxena D, Mavalankar D (January 2021). "Vitamin D supplementation, COVID-19 & Disease Severity: A meta-analysis". QJM : Monthly Journal of the Association of Physicians. 114 (3): 175–181. doi:10.1093/qjmed/hcab009. PMC 7928587. PMID 33486522.
- 199) Stroehlein JK, Wallqvist J, Iannizzi C, Mikolajewska A, Metzendorf MI, Benstoem C, et al. (May 2021). "Vitamin D supplementation for the treatment of COVID-19: a living systematic review". The Cochrane Database of Systematic Reviews. 2021 (5): CD015043. doi:10.1002/14651858.CD015043. PMC 8406457. PMID 34029377. S2CID 235202971.
- 200) Cesareo R, Falchetti A, Attanasio R, Tabacco G, Naciu AM, Palermo A (May 2019). "Hypovitaminosis D: Is It Time to Consider the Use of Calcifediol?". Nutrients (Review). 11 (5): 1016. doi:10.3390/nu11051016. PMC 6566727. PMID 31064117.
- As of May 16, 2022, the VitaminDWiki page had: 34 trials, 10 trial results, 36 meta-analyses and reviews, 69 observations, 38 recommendations, 55 associations, 89 speculations, 58 videos, 45 Mortality studies see related: Governments, HealthProblems, Hospitals, Dark Skins, 26 risk factors are ALL associated with low Vit D, Recent Virus pages Fight COVID-19 with 50K Vit D weekly Vaccines Take lots of Vitamin D at first signs of COVID
- Treatments for 303,000 COVID-19 patients: vitamin D is both popular and over-the-counter – May 2021
- Those getting high dose vitamin D were 7 X less likely to die of COVID-19 - Dec 11, 2020
- French Consensus – 200,000 IU of Vitamin D if get COVID-19 – Dec 22, 2020
- COVID-19 patients getting 300,000 IU of Vitamin D were 5X less likely to die – Sept 2021
- A single dose of 300,000 IU of vitamin D should fight COVID-19 for 2 months - Hypothesis - Aug 21, 2020
- COVID-19 mortality extrapolates to zero at 50 ng of vitamin D – 18th Meta-analysis Sept 2021
- COVID-19 risk reduction by early treatment: 5X Vitamin D – Oct 8, 2021
- Emergency treatments if get COVID-19 symptoms - Oct 2021