Avoid multivitamins like the plague, they are the ONE supplement most commonly ingested by the most people(quick and easy...) and there appears to be some rather valid links to cancer(if DS were to fuck with one thing....)

Vitamin D and Zinc together with Quercetin or Cloroquinine or Ivermectin(all of them zinc ionophores, meaning they help get zinc into your cells so any one of them should be taken with zinc, zinc increases the strength of cell membranes and thus increase your cells resistance to things)

Vit D/Zinc/ and any of the ionophores(I use quercetin) is the best bet for boosting your immune system, magnesium(magnesium oxide/citrate is preferable, stuff like magnesiumhydroxide often have digestion/absorption issues) is also a good idea as in addition to being involved in cell.division, nerves(ever have cramps, not enough magnesium and...) it helps maintain electrolyte balance which means keeping you hydrated and together with D are the 2 people are the most commonly deficient in(Zinc is still under researched but there are indications it also belong on the list)

People tend to underestimate the use of hand-sanitizer but 95+% of all bacterial and viral transfer into humans are contact spread(shopping cart handles, door handles, stair-rails...).

I'm very rarely sick and basically get a flu/cold drive-by every 3'ish years(start feeling something in the evening, sick day 2 and getting better towards the evening and basically functional again on day 3.... and that is the worst-case, usually day 2 isn't that bad), anyway...

Face diapers were obviously a waste but started using hand sanitizer when all of this shit started, recently had a drive-by and that was at least 2 years overdue..............