Randomised trial shows that Vitamin D keeps most Covid19 patients out of ICU.
Our pilot study demonstrated that administration of a high dose of Calcifediol or 25-hydroxyvitamin D, a main metabolite of vitamin D endocrine system, significantly reduced the need for ICU treatment of patients requiring hospitalization due to proven COVID-19. Calcifediol seems to be able to reduce severity of the disease, but larger trials with groups properly matched will be required to show a definitive answer.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456194/pdf/main.pdf