Vitamin D

A major randomized trial led by Mass General Brigham found that a four-week course of high-dose vitamin D3 started soon after a positive COVID-19 test did not reduce acute illness severity, healthcare visits or deaths, and did not curb household spread. But in an analysis limited to participants who consistently took the assigned pills, researchers observed a small, borderline statistically significant difference in lingering symptoms reported eight weeks after infection, a finding they say warrants further study.