Can it be predicted how many vaccinated people need to be infected before Covid becomes more vaccine resistant

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?

Early days yet, but generally speaking vaccines which rely on exposing the immune system to just some parts of a pathogen (like BionTech, Moderna, Astra Zeneca, Sputnik V) tend to be more susceptible to variants than whole Virus vaccines.
We have seen some evidence of that, the aforementioned vaccines are essentially worthless with one shot against the Delta variant (versus about 80% or so for the wild pathogen) and about 60%-70% effective with two shots (95% for two shots for wild disease).

Not seen any published numbers but the whole virus vaccines seem to have maintained efficacy at around the same levels (70%) even with the new variant numbers, going by outbreaks in Chile and Indonesia.

With numbers context is important Pfizer, Moderna trials only reported symptomatic cases while some of the much reported low efficacy Chinese vaccines numbers included asymptomatic and mildly symptomatic cases.

That said I was a betting man, I would say prepare for needing boosters within a year or so.

It seems to me like the OP might be slightly confused with regards to the causality here. More vaccinated people doesn’t make it more likely that the virus will mutate into a vaccine-resistant strain. It makes it less likely. There’s a chance of mutation at every instance of virus replication, and the nature of those mutations is pretty much random. Whether they’re helpful or harmful to the virus, with or without regards to vaccines, is a matter of chance. More vaccinated people equals fewer infections equals fewer rolls of the mutation dice equals less chance of a mutation that results in vaccine resistance.

However, if a vaccine-resistant mutation does occur, high numbers of vaccinated people make it more likely that the ensuing strain will become the dominant one, even if it would less virulent than competing strains in an unvaccinated population.

Wouldn’t antibodies produced by a vaccine create selection pressure for the virus to evolve in ways that make it resistant to vaccine produced antibodies?

I believe the mRNA vaccines are about 66% effective at preventing infection from Delta covid. Which is better than nothing, but it still means endless millions will catch the virus even with a vaccination. This gives the virus a chance to mutate in an environment with antibodies.

1.66% effective at symptomatic covid. They are probably substantially less effective at preventing asymptomatic infections and much much more effective in preventing hospitalisation and disease.
2. A mutation which can defeat all vaccines is….nothing special. Probably many such variants about now.What’s problematic would be one which can defeat all vaccines AND is as infectious and causes similar or higher morbidity.

And in a major “FUCK” out of Israel is seems that Pfizer efficiency drops for two shots drops into the teens at 6 months or so.
@Alessan when did you get vaccinated?

The virus will mutate both among vaccinated and unvaccinated, with the latter group being far more likely to produce a vaccine-beating strain. Mutations are defective attempts to make copies of itself. They’re actually ‘mistakes’, accidents. Most of these defective copies are just that - defective. They end up being duds that harm nobody. But when you have millions upon millions of new infections, a few of those copies are going to have the ability to put pressure on the vaccine regime. First through more efficient transmissibility, and then some variants might have the added ability to get around antibodies and either overwhelm the immune system through sheer viral load or perhaps stealthily attacking the immune system in other ways.