A new article has just been published in the Journal of Steroid Biochemistry and Molecular Biology looking to see if an oral vitamin D supplement can be used to cure covid-19. Considering that vitamin D is cheap, widely available, and safe, it would be pretty miraculous if that turned out to be the case.
A new study has just been published in JAMA (the Journal of the American Medical Association) that seeks to answer this question definitively. This subject has been somewhat controversial, because observational studies have tended to show a positive effect, while randomised clinical trials have failed to show any effect. Usually you would trust the trial data more than the observational data, but these trials were all relatively short (generally a year or less), had relatively small study groups, and often used quite low doses of vitamin D.