A little vitamin C and vitamin D3 will probably do it for most people.
I should add that I’m not a doctor, so everyone should consult professional care and decide for themselves.
We have been taking D3 and K2. Also drinking the airborne vitamin C with zinc. I know there is a lot of exaggeration in the numbers but covid-19 is still quite a serious disease to those with impairments. Diabetes, COPD, and other health issues