Here’s what my internal medicine guy recommended:

4,000 units of D3
30Mg of Zinc
250Mg of Quercetin
500Mg of Vitamin C

He recommended taking this daily along with eating right and exercise. He indicated that masks were essentially worthless outside of a clinical setting and only wore one to keep the nurses in his office from bitching at him. All of the things listed are clinically proven prophylactics against Corona viruses. He has been frustrated that these simple preventive measures haven’t been touted in the media which has been more focused on testing and treating instead of prevention.