[kmonad]

I think the hospital capacity is a key argument indeed. But there is another aspect to consider. Each viral replication is a potential event where a new variant can arise, thus the fewer viral replications the better since each new variant has unknown risks. An unvaccinated person will on average be host to many more viral replications after exposure to the virus than a vaccinated person after exposure. Thus, if a large part of the population remains unvaccinated, the virus has more room room to evolve than necessary given we have easy access to effective and safe vaccines. Therefore, this should also factor into a debate around vaccination policies and personal choice vs societal risk.

[mikem170]

> Thus, if a large part of the population remains unvaccinated, the virus has more room room to evolve than necessary given we have easy access to effective and safe vaccines.

Word was that Omicron diverged from an earlier version of covid in mice, over the course of about a year, then jumped into humans [0].

I think this detracts quite a bit from the point you were trying to make above, since we are not vaccinating mice, nor all the other animals that harbor covid such as bats, cats, dogs, primates, and deer [1].

Since we can't vaccinate or destroy all of the non-human hosts for this coronavirus, and the virus already has evolved in animals and made the jump to humans a couple of times, I don't agree that the point you made above is relevant.

[0] https://www.medicalnewstoday.com/articles/covid-19-did-omicr...

[1] https://www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/...

[kmonad]

Interesting. Indeed animal hosts could be problem. I would counter two points:

1) Assuming animals were a major source of variants, it quantitatively but not qualitatively changes the problem. Until we know the quantities, I do not see how you can assert relevance.

2) The references you provide say Omicron came most likely from a human with prolonged infection. The paper proposing a intermediate variant in mice is interesting, but considered unlikely (your reference: "Evolutionary biologist Mike Worobey, Ph.D., of the University of Arizona in Tucson, said the most plausible theory remained that Omicron evolved in an immune-compromised patient with a protracted [SARS-CoV-2] infection.")

Viral replications are the only scenario where variants can emerge naturally. Duration of disease and severity of disease are correlated with load and total viral replications. Vaccination reduces both at the population level. A vaccinated person therefore will on average be a less likely source of a variant. How much this weighs against other factors when deciding on policy is impossible for me say, but I would insist it is not irrelevant based upon current knowledge.

[mikem170]

I would agree that it is not irrelevant. My language there may have been too strong.

I was probably thinking that the other factors (personal protection, hospital capacity, and the political question of mandates) seem so much more significant to me. There's lots of lesser factors (side effects, the immuno-compromised, social cohesion, etc).

I guess I kind of looked at variants as a wash, given they are so much out of our control and there are many unknowns. It's in the realm of possibility that the current vaccines could leave us more susceptible to future variants (a la original antigenetic sin). Hard to make a decision on less significant unknowns.

[nradov]

I encourage everyone eligible to protect themselves by getting vaccinated but this is unlikely to prevent new variants from evolving. The current thinking is that new variants are most likely to evolve in immunocompromised patients who experience prolonged infections. Vaccines are less effective for them.

https://www.scientificamerican.com/article/covid-variants-ma...

[kmonad]

I agree with this, and I do not think it contradicts my original statement. You cannot prevent new variants, but you can reduce the rate of their emergence.

The paper you cite supports this: in a case study of a single immunocompromised patient who---because of that---had a prolonged infection, many replications of the virus were observed. This patient represents a "hot spot" of variant emergence in this furthermore antibody treated patients. From the article "the remaining samples [sic: most] are consistent with arising from a consistent viral population".

What I take from this is: we ought to prevent prolonged infections where it is possible. Again, from the article "The effects of convalescent plasma on virus evolution found here are unlikely to apply in immunocompetent hosts in whom viral diversity is likely to be lower owing to better immune control." And a vaccinated individual will on average have the best immune control.

[nradov]

We don't do anything to reduce the rate of emergence of new variants of HCoV-OC43, another betacoronavirus very similar to SARS-CoV-2 in terms of genetics and clinical effects. So far that hasn't been a problem.

https://www.sciencedirect.com/science/article/pii/S026240792...

[kmonad]

That virus has also not caused a global, multi-year long pandemic. In this context, your reference seems tangential to me. Vaccinations ought to reduce SARS-CoV-2 variant emergence rates by virtue of reducing viral replications.

[nradov]

What are you talking about? As far as we can determine, HCoV-OC43 did cause a global, multi-year long pandemic starting in 1889.

[kmonad]

Lol, right---I did not recognize this as the agent of one of the "deadliest pandemics" starting in 1889 (Wikipedia) in history. But what is your point? Are you of the opinion that vaccines cannot reduce variant emergence rates?