Thread by @yaneerbaryam

There are some that haven't understood the science behind the selection of vaccine evading variants.

This may help:

This is the same as what happens in your body if you only take part of the antibiotics prescribed for an infection --- antibiotic resistant strains arise.

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https://twitter.com/yaneerbaryam/status/1436036842193920000

This is also the reason for the appearance of antibiotic resistant pathogens. When we use antibiotics to inhibit but not eliminate a pathogen, the pathogen evolves to become resistant to that antibiotic.

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A technical term used for this discussion is "imperfect vaccines" i.e. vaccines that don't completely stop infection.

Looking in google scholar gives many papers on this subject

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scholar.google.com/scholar?hl=en&…

One study: Imperfect vaccines and the evolution of pathogen virulence

"Vaccines rarely provide full protection from disease. Nevertheless, partially effective (imperfect) vaccines may be used to protect both individuals and whole populations.

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nature.com/articles/41475…

"We studied the potential impact of different types of imperfect vaccines on the evolution of pathogen virulence (induced host mortality) and the consequences for public health. Here we show that vaccines designed to reduce pathogen growth rate and/or toxicity diminish

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"..selection against virulent pathogens. The subsequent evolution leads to higher levels of intrinsic virulence and hence to more severe disease in unvaccinated individuals. This evolution can erode any population-wide benefits such that overall mortality rates are unaffected

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"..or even increase, with the level of vaccination coverage. In contrast, infection-blocking vaccines induce no such effects, and can even select for lower virulence.

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Another Study: "Imperfect vaccines and the evolution of pathogens causing acute infections in vertebrates

"use of either antigrowth or antitransmission vaccines leads to the evolution of pathogens with an increased within-host growth rate;

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onlinelibrary.wiley.com/doi/pdfdirect/…

"..infection of unvaccinated hosts with such evolved pathogens results in high host mortality and low pathogen transmission. Vaccination of only a fraction of hosts with antigrowth vaccines may prevent pathogens from evolving high virulence due to pathogen adaptation ...

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"..to unvaccinated hosts and thus protection of vaccinated hosts from pathogen-induced disease. In contrast, antitransmission vaccines may be beneficial only if they are effective enough to cause pathogen extinction.

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"..Our results suggest that particular mechanisms of action of vaccines and their efficacy are crucial in predicting longterm evolutionary consequences of the use of imperfect vaccines."

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Relevant article on vaccine evasion in another context

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cidrap.umn.edu/news-perspecti…

Another useful article:

"...more robust to pathogen evolution because they limit replication and reduce the opportunities for spread to new hosts"

So if you don't stop spread, you don't prevent evolution.

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royalsocietypublishing.org/doi/10.1098/rs…