Yes, COVID replicates in the nose quite a bit pre-symptoms but for it to out-compete the actual very fit active strains, which are turning your upper respirator

Yes, COVID replicates in the nose quite a bit pre-symptoms but for it to out-compete the actual very fit active strains, which are turning your upper respiratory tract into a virus factor, it would be difficult to ensure no symptoms. Also, of course you are only a few mutations away at any one time from an unpredictably virulent version; there is no guarantee that the trajectory of viral evolution is toward less virulence. > The thing you are after is a virus that has same basic spike protein for your immune system to recognize and only enough mechanism to multiply itself. The version of that that is feasible is a viral vector vaccine e.g., ChAdOx1.