Ignoring stuff that should be said, Zinc and Vitamin D3 (yes, ONLY D3) are essential to avoid (or lessen the effect) of any cold virus as they improve the immune system. Another supplement to use if you want to avoid any type of Corona virus is Agarikon mushrooms because they naturally blunt the "hooks" (the part for which these cold viruses are called "Corona" since they make them look like little suns). If the hooks are bent or damaged, then they are unable to attach themselves to you. Here's where I get mine though they are also available on Amazon. They come from a well-known Mycologist named Paul Stamets who is just up the road from me.
https://www.swansonvitamins.com/fungi-perfecti-host-defense-agarikon-60-veg-caps
Getting outside in the sun is the best way to get Vitamin D naturally.
My addendum was primarily targeting allergies and I forgot to mention one that is extremely useful! Raw, unfiltered and, preferably, local bee honey! Among the zillions of positives for honey (which include the fact that it's the only known food that never spoils and the only sugar that's safe to ingest in reasonable, one to two tablespoon per day quantities), it is awesome for getting your body used to outdoor pollens.