The current vaccines don't prevent infection, reinfection, or transmission -- which eliminates much of the selective pressure for lower mortality. We could end up with a situation where everyone alive on earth is vaccinated, carries the virus, receives regular boosters, and anyone who isn't or who misses a few boosters, faces certain death. Similar to Marek’s disease in chickens.

I'm not sure, but I think the problem is that nobody cares enough about chicken to develop a better vaccine. How much would it cost? Can someone here pay for it so we can remove that scary story in Wikipedia?

Current vaccines are effective at infection prevention. For modRNA vaccine, it's around 80% after 6 months.

Transmission seem to be recuded only for 2 months after vaccination.

Nothing completely prevents infection, but vaccines are the best way to mitigate it.

> Under normal conditions, highly virulent strains of the virus are not selected. A highly virulent strain would kill the host before the virus would have an opportunity to transmit to other potential hosts and replicate. Thus, less virulent strains are selected. These strains are virulent enough to induce symptoms but not enough to kill the host, allowing further transmission. However, the leaky vaccine changes this evolutionary pressure and permits the evolution of highly virulent strains.[13] The vaccine's inability to prevent infection and transmission allows the spread of highly virulent strains among vaccinated chickens. The fitness of the more virulent strains is increased by the vaccine.

https://en.wikipedia.org/wiki/Marek%27s_disease#Prevention

Following the references, it all seems solid; the referenced authors note this hasn't been observed for human viruses yet (2017), but posits non-sterilizing vaccines in humans might be too new.

On the other hand, it seems like a kind of inverse prisoners' dilemma.

If no one vaccinates, this particular pathway for the evolution of super-viruses is closed (although others remain open). If some people vaccinate, and a super-virus evolves, they're fine and the rest are screwed, classic P.D.

But it deviates where unlike the classic P.D. where things get worse if everyone defects, once everyone vaccinates, it doesn't matter if a super-virus evolves, because everyone is protected.

So while this raises an interesting policy question on whether non-sterilizing vaccines are worth the risk, once people begin "defecting" by getting vaccinated, it seems like a bad move to risk staying unvaccinated yourself.

This is not true. COVID-19 is unusual because symptoms don’t tend to develop until the second week of the infection, by which time most of the active virus has been neutralized by the body’s immune response.

Unlike most viruses, COVID-19 does not have the same selective pressure to become less deadly.

> History shows that as a Virus mutates and evolves they tend towards more transmissibility but lower morality rate.

This isn't guaranteed, there are plenty of viruses that are still cause severe illness despite being around for quite some time. It's entirely possible that the virus mutates to be more lethal[1], as well.

And if mortality does decrease, it could take many human lifetimes before such an equilibrium is reached. In the meantime, the virus can mutate, wreak havoc and kill a lot of people.

It's also important to point out that virus evolution depends on selection pressures, and one of the selection pressures for decreased viral lethality is a severe reduction of host organisms that the virus can replicate in. That is to say that the selection pressure that causes a virus to be less lethal can very well be the eradication of large populations of host organisms.

[1] https://www.usatoday.com/story/news/factcheck/2021/07/14/fac...

What viruses have mutated to be significantly more deadly?

I was curious so I looked it up and found:

https://www.usatoday.com/story/news/factcheck/2021/07/14/fac...

The examples they give in the article are Ebola in 2016, West Nile Virus in 1999, and the Spanish flu in 1918.

Yep. From what I’ve read we are waiting for the “common cold” version of Covid. Where it dominates, is an inconvenience, and we can just live with it.

I don’t think this helps much. We know that mortality rate has not been incredibly high even for the original variant, but it managed to overwhelm the medical facilities of nations regardless. Unless the mortality rate drops dramatically, down to what’s observed with eg the flu, it’s still concerning.

Covid is actively being stopped from evolving however because of vaccines and because, you know, we don't just let infected people die. Deaths are usually in people with preexisting conditions. In this context , why will the virus evolve a milder version? It seems strict isolation of the infected might help

If that was the case we would’ve been wiped off as a species 40 years ago as the seasonal flu mutated into a super virus.