The Government should fund wider clinical trials of vitamin D / calcifediol in UK hospitals now. Studies have found some positive effect, but they also concluded that further and larger trials are needed to properly understand the benefits of this potential treatment.
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Clinical studies have suggested that the use of calcifediol, or of vitamin D containing regimens, could make Covid-19 patients in hospital less likely to require intensive care treatment and ICU admission. The trials also did not find any evidence of side-effects from vitamin D / calcifediol.
https://www.sciencedirect.com/science/article/pii/S0899900720303002
https://www.sciencedirect.com/science/article/pii/S0960076020302764