The vitamin D endocrine system have a variety of actions on cells and tissues involved in COVID-19 progression.
Early calcifediol (25-hydroxyvitamin D) treatment to hospitalized COVID-19 patients significantly reduced intensive care unit admissions-Calcifediol seems to be able to reduce severity of the COVID-19.
Calcifediol seems to be able to reduce severity of the disease.
https://www.sciencedirect.com/science/article/pii/S0960076020302764