As far as I can gather this claim stems from a single non-peer reviewed preliminary report from back in may: https://www.webmd.com/lung/news/20200518/more-vita

As far as I can gather this claim stems from a single non-peer reviewed preliminary report from back in may: https://www.webmd.com/lung/news/20200518/more-vitamin-d-lower-risk-of-severe-covid-19 https://www.webmd.com/lung/news/20200518/more-vitamin-d-lowe... https://www.yalemedicine.org/stories/vitamin-d-covid-19/ https://www.yalemedicine.org/stories/vitamin-d-covid-19/