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.
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COVID-19 treated by Vitamin D - studies, reports, videos
- As of April 29, 2022, the VitaminDWiki COVID page had: 19 trial results, 37 meta-analyses and reviews, Mortality studies see related: Governments, HealthProblems, Hospitals, Dark Skins, 26 risk factors are ALL associated with low Vit D, Fight COVID-19 with 50K Vit D weekly Vaccines Take lots of Vitamin D at first signs of COVID 126 COVID Clinical Trials using Vitamin D (March 2023) Cost to prevent a COVID death: 11 dollars of Vitamin D - Nov 2022
5 most-recently changed Virus entries
- 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