I use chelated zinc with quercetin: 30 mg zinc once/day and 250 mg quercetin BID.
That’s in addition with vitamins A, Bcomplex, C and D3. Also iodine.
After decades of one illness after another, I haven’t had any meaningful viral infection for over 2 yrs.
Most people have excess vitamin A. Vitamin A stores increase with age. There is a ridiculous amount of foods with added vitamin A.