I've had nothing more serious than a 'throat tickle' (I don't really know how else to describe that gross feeling I get in the back of my throat when I know I've been infected with a cold/flu bug) for the last 3 years. I've been supplementing with D and zinc during the bottom half of the year and adding quercetin and NAC when I feel a 'bug'. No Covid shots and no tests so far. I don't consider either of those things to be useful.