“In a Spanish randomized controlled trial (RCT), high-dose vitamin D (100,000 IU) reduced the risk of requiring intensive care by 96%”

(vitamin D) Castillo, M.E., Costa, L.M.E., Barrios, J.M.V. et al. Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study. The Journal of Steroid Biochemistry and Molecular Biology. October 2020. https://doi.org/10.1016/j.jsbmb.2020.105751.