Joe Rogan had Dr Rhonda Patrick on a few days ago and gave a detailed rundown of the research into vitamin D vs Covid/respiratory illness in general, among other topics (timestamped to the start of Vitamin D talk but the whole podcast is definitely worth a listen)

https://youtu.be/4_ZJ8YDOX6g?t=1771

Vitamin D insufficiency has been strongly correlated to COVD-19 deaths and severe symptoms in various locations, although obviously more data is still needed to prove causation.

Either way unless you work outside you should probably be on 5000 IU of Vitamin D a day just to compensate for sunlight deprivation.