> There is emerging evidence to suggest that vitamin D deficiency is associated with adverse outcomes in COVID-19 patients. Conversely, vitamin D supplementation protects against an initial alveolar diffuse damage of COVID-19 becoming progressively worse.
Looks like Joe Rogan's advice was on the money
I'm not sure that Joe Rogan can claim much credit here - I just Googled to check when 'Joe Rogan' mentioned Vitamin D and it seemed to be mid May - by then us lot in Europe had already stripped the shelves of Vitamin D for a couple of months!