the point of all virus protection mechanisms is to *reduce the probability of infection* period.
as anyone mathematician knows in elementary probability, the layering of several defense mechanisms multiply the protective effect.
to propose a worst case, once size fits all protective mechanism against virus, is counter productive, potentially damaging (making the cure worse than the disease) and will fail due to impracticability anyway.
that is why multiple effective measures like, sanitizer, hand washing, mask, social distancing under certain conditions, etc., etc, all layer up to make for a near 100% effect.
“as anyone mathematician knows in elementary probability, the layering of several defense mechanisms multiply the protective effect.”
As every engineer knows, you don’t spend money trying to make very small risks slightly smaller.