No clinical trials ? Bioqr posted about vitamin d3 studies recently https://www.bostonherald.com/2020/09/17/vitamin-d-can-help-reduce-coronavirus-risk-by-54-boston-university-doctor/ First, that article isn't a clinical trial. Second, people who are vitamin deficient are less healthy, and this might be due to poor diet and or underlying health issues or even old age. Providing vitamin and nutrient supplements may indeed help such people, and that isn't surprising, but it is hardly a cure for Covid-19 infection.