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Originally Posted by opendoor
But you need to be careful with how you put it. Yes, vaccines or prior immunity generate selective pressure on mutations that evade immunity, simply because anything that doesn't evade immunity is dead in the water. However, because mutations are random, prior immunity reduces the number of problematic mutations that are viable.
With little to no existing immunity, a virus just needs to mutate to become more severe without impacting its ability to spread and then you have a very real risk of a more severe variant taking over. That's what happened with prior variants. Once you have widespread immunity though, the virus needs to mutate to become more severe AND mutate in ways that it can evade immunity. That's a significantly higher threshold to clear, as immune evasion requires a fairly significant number of mutations generated through an iterative process of cumulative errors.
And this isn't just a theoretical thing; studies have found an inverse correlation between vaccination rates and the mutation frequency in SARS-CoV-2. As well as a significantly reduced mutation frequency in people with prior immunity, as immunologically naive people who get infected exhibit more mutational variance than vaccinated/previously infected people.
So yes, immunity will favor selection of immune evasive variants; that's obvious and it would be the case even vaccines were 100% effective. But the threat of more severe variants popping up is reduced with a higher level of immunity.
I mean less diversity. Alpha, Beta, Delta, and Gamma all existed by September of 2020, after there were ~100 million cumulative infections. Since Omicron took over, we've probably had 10-20x that many infections (including a vast number in people with some form of prior immunity), yet the currently circulating variants are still less distinct than the variants that popped up in the first 6-8 months of widespread infections.
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What studies have shown that Covid is likely create a more deadly virus in an unvaccinated person? That was likely true back in 2021, when the unvaccinated were far more likely to catch covid. Now with the current strains vaccinated people are just as likely to catch covid.
https://www.healthline.com/health-ne...s-unvaccinated
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“They play a huge role. If everyone is vaccinated, eventually infections drop to zero and so do variants,“ Parikh said. “But if the virus has an easy host, such as an unvaccinated individual, then it is easy for it to mutate into a more contagious and virulent form.”
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This simply is not true anymore as vaccination provides only a very small amount of protection against actually catching current Covid strains.
Also, what evidence is there to show that Covid will mutate into a more deadly strain. The evolutionary pressure is for the opposite. Also viruses that are extremely similar to Covid-19 account for about 15% of common colds. Why is Covid-19 more likely than these existing viruses, that infect us all the time, to revert into some ultra deadly strain?