[opendoor]

Originally Posted by blankall

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

This simply is not true anymore as vaccination provides only a very small amount of protection against actually catching current Covid strains.

For the reasons I outlined above:

1) Fewer replications in people with prior immunity means fewer opportunities for mutations.

2) Fewer pathways for it to mutate and be viable. For a mutation to thrive now, it has to overcome existing immunity, which is a pretty significant threshold to clear. With an immunologically naive population, that's not a concern. It just has to be able to spread effectively and it can potentially become the dominant variant.

This study is from 2021, but it's comparing infected vaccinated vs infected unvaccinated (e.g. immunologically naive), so any protection against infection is irrelevant. We're talking about what happens after being infected:

Prospective validation of these macroscale evolutionary patterns using clinically annotated SARS-CoV-2 whole genome sequences confirms that vaccine breakthrough patients indeed harbor viruses with significantly lower diversity in known B cell epitopes compared to unvaccinated COVID-19 patients (2.3-fold, 95% C.I. 1.4-3.7).
...
This study presents the first known evidence that COVID-19 vaccines are fundamentally restricting the evolutionary and antigenic escape pathways accessible to SARS-CoV-2.

https://www.medrxiv.org/content/10.1....01.21259833v1

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?

There isn't really any evolutionary pressure to become less severe in a disease that takes as long as COVID does to debilitate. People die weeks after infection, so if it kills 0.1% of those it infects or it kills 5%, it doesn't really affect its ability to spread other than through how we mitigate it in response to its severity. Or to put it another way, why would the less severe variant out-compete a more severe one if both were circulating at the same time?

As to why other coronaviruses don't mutate to become deadly, there are a couple of reasons:

1) They're not as transmissible and they're not nearly as severe. So fewer opportunities to mutate and when they do, they would have to become essentially a fundamentally different coronavirus to get anywhere near the severity of COVID. The only likely way that would happen is through recombination with a more severe coronavirus, but the chances of that are very, very slim.

2) Decades/centuries of prior immunity which helps slow down the rate of mutations for the reasons outlined above (which is my whole point).

To get back to my main point, I was responding what you said here:

Originally Posted by blankall

having immunity actually encourages mutations, for the same reason that antibiotics breed mutations.

That's simply not correct. Immunity (whether through infection or vaccination) does not encourage mutations. There is selective pressure to evade immunity (as there is with any virus), but that doesn't mean it happens at an increasing rate. Overall, widespread immunity tends to reduce the rate and diversity of mutations.