The immune system does not work that way. When you present an antigen to it, it trains a variety of antibodies to different sites on the antigen, and these anti

The immune system does not work that way. When you present an antigen to it, it trains a variety of antibodies to different sites on the antigen, and these antibodies are slightly different for every person. It's as if instead of taking one antibiotic against a bacterial infection, you took many slightly different ones at the same time, and every treatment of antibiotics differed. Obviously, bacteria are much less likely to develop resistance that way. Vaccine evasion can happen if the virus mutates so much it's almost unrecognizable (flu) or if the vaccine is too narrowly targeted and it presents not enough sites for the immune system, so a single mutation is enough for immunity. The former apparently doesn't apply to Covid**, the latter basically never happens - the old dead/weakened methods avoided this by design, while the newer methods learnt to watch out for this and present enough of the virus. * Mutations kept the spike. There were several mutations that changed it so there's a limited level of evasion from vaccine and natural immunity (Beta, Kappa), but these mutations apparently strongly hurt the ability to spread, so much that these variants seem to decline naturally before reaching epidemic status.