My understanding is that about 2 billion humans have been vaccinated, but even the 2 dose mRNA vaccines only reduce the chance of infection from Delta by maybe 2/3 (however the vaccines are far more effective at preventing severe disease, hospitalization and death). So theres going to be a lot of infections in vaccinated people.
Can it mathematically be determined how many vaccinated people need to be infected before the virus mutates and develops a spike protein that is more resistant to the vaccine?
Also if the vaccine means you’re more likely to get a mild or asymptomatic illness, does that mean your body is producing far fewer viral particles and as a result, far fewer chances of infection? I’m not sure how many covid viruses your body makes, but as an example if you get a common cold doesn’t your body eventually produce several hundred trillion viral particles between the first sign of infection and when the infection is over? Would vaccinated people only produce a fraction of the normal number due to fewer infected cells and the virus clearing up faster? An unvaccinated person who produces (as a guess) a quadrillion viral particles has more chances for mutation than a vaccinated person who maybe (as a guess) only produces 100 trillion viral particles.
Basically, is there a reasonable ability to predict that X number of vaccinated people need to catch Delta before genetic mutation Y that reduces the effectiveness of a vaccine by a meaningful amount is evolved?
Also does it depend on the vaccine? Will mutations that work against the AZ vaccine also work against the pfizer vaccine, or are the antibodies slightly different?