5 ms·

I think we should thank whatever god that so far it seems we didn't end up with a Marek's disease type situation. I don't know how much of a guarantee there was

I think we should thank whatever god that so far it seems we didn't end up with a Marek's disease type situation. I don't know how much of a guarantee there was about this with covid, but if the vaccine would have promoted a much more aggressive virus we could have ended up in a situation where any unvaccinated human will basically die (this happens in chickens, see: https://en.wikipedia.org/wiki/Marek%27s_disease https://en.wikipedia.org/wiki/Marek%27s_disease). I sincerely hope the people who devised this vaccine know what they are doing. As far as I know (according to a Katalin Kariko inteview), the Sars-Cov-2 spike protein can't mutate too much without limiting it's effectiveness, so therefore this vaccine should theoretically work in the future. But that Marek's disease issue is very very scary to me.

r00fus 5y ago
DOesn't the problem with Marek's disease have more do do with the horrendous conditions of poultry handling worldwide (mainly close confines)? I don't think that's generally transferrable situation unless you consider humans to be under similar conditions.
isoprophlex 5y ago
Well... that was an unsettling read. > The evolution of Marek's disease due to vaccination has had a profound effect on the poultry industry. All chickens across the globe are now vaccinated against Marek's disease (birds hatched in private flocks for laying or exhibition are rarely vaccinated). Highly virulent strains have been selected to the point that any chicken that is unvaccinated will die if infected.[14] Other leaky vaccines are commonly used in agriculture. One vaccine in particular is the vaccine for avian influenza. Leaky vaccine use for avian influenza can select for virulent strains.[15] Wonderful. Like H5N1, which has a 60% mortality in humans.
- collegeburner 5y ago
  I remember it was discussed months ago on HN when early on in vaccines roll out, somebody raised this concern but the consensus was the vaccines mostly prevented infection so not a big worry ¯\_(ツ)_/¯
  - jl6 5y ago
    The Marek scenario occurs when a vaccine removes the evolutionary pressure against more virulent strains. The actual mutation event that creates the more virulent strain occurs randomly. Whether that variant survives and thrives depends on all of the evolutionary pressures in force. If a strain is so virulent that it kills the host, it is selected against, because the dead can't spread. If a vaccine lets the host survive but does nothing to stop transmission, that negative evolutionary pressure is gone. Thus, the potential for a vaccine to drive the propagation of a more virulent strain if all other things are equal. However, there's good reason to believe that all other things will rarely be equal. The survival rate of the host is just one selection pressure. Anything can be a selection pressure if it has an impact on reproductive success of a subset of the population. It's possible that increased host survival is a very tiny or even zero pressure - for example, if the virus has a long contagious period, it might have already done all the spreading it's going to do before onset of symptoms and death, rendering survival time irrelevant. Other pressures could dominate - for example, the virus could be susceptible to being killed by sunlight, favoring variants with a light-insensitivity property over variants with a virulence property. One could even imagine how host symptoms could create positive pressure towards virulence - for example, more coughing and bleeding could help transmission. Such a virus would have its survival chances reduced by a leaky-but-symptom-reducing vaccine, and increased by vaccine-avoidance. Evolution is spectacularly multi-dimensional. None of these outcomes are inevitable.
  - Izkata 5y ago
    That was an especially frustrating period. The vaccine trials never tested for that, and later studies were all like "maybe it does", so the sars-cov-2 vaccines preventing infection was always misinformation and no one was willing to accept that. At least people are aware of it now I guess?
edmundsauto 5y ago
> I sincerely hope the people who devised this vaccine know what they are doing. I think we all hope this. I can say that I sincerely believe the people who devised the vaccine know a hell of a lot more than just about anyone else on the planet. I don't trust experts in economics or socio-politics, but I do trust experts in virology. Not to say their information is perfect, but they know so much more than other people in a field where expertise is connected to outcomes.
- cloutchaser 5y ago
  The people who said vaccines will prevent infection and spreading of Covid?
  - edmundsauto 5y ago
    Nuance matters here. Vaccines do prevent the spread, it's just not 100%. Are you a Bayesian? If so, using the prior of "vaccines are pretty effective at preventing spread" was reasonable until new data came in - this was a brand new technique in a novel virus. Further, the environment changed due to mutations - the fair question is "how effective was the vaccine at preventing the spread of the origin virus?"
reducesuffering 5y ago
Man, I regret reading this. The cynic in me immediately jumps to a possible world is where a pharmaceutical company is incentivized to bring about a world where every human needs a Medicine-as-a-Service to not die. The world's greatest $ printer.
- cloutchaser 5y ago
  To be fair they already have this with polio, mumps, rubella and others.

r00fus 5y ago

DOesn't the problem with Marek's disease have more do do with the horrendous conditions of poultry handling worldwide (mainly close confines)? I don't think that's generally transferrable situation unless you consider humans to be under similar conditions.

isoprophlex 5y ago

Well... that was an unsettling read. > The evolution of Marek's disease due to vaccination has had a profound effect on the poultry industry. All chickens across the globe are now vaccinated against Marek's disease (birds hatched in private flocks for laying or exhibition are rarely vaccinated). Highly virulent strains have been selected to the point that any chicken that is unvaccinated will die if infected.[14] Other leaky vaccines are commonly used in agriculture. One vaccine in particular is the vaccine for avian influenza. Leaky vaccine use for avian influenza can select for virulent strains.[15] Wonderful. Like H5N1, which has a 60% mortality in humans.

collegeburner 5y ago
I remember it was discussed months ago on HN when early on in vaccines roll out, somebody raised this concern but the consensus was the vaccines mostly prevented infection so not a big worry ¯\_(ツ)_/¯
- jl6 5y ago
  The Marek scenario occurs when a vaccine removes the evolutionary pressure against more virulent strains. The actual mutation event that creates the more virulent strain occurs randomly. Whether that variant survives and thrives depends on all of the evolutionary pressures in force. If a strain is so virulent that it kills the host, it is selected against, because the dead can't spread. If a vaccine lets the host survive but does nothing to stop transmission, that negative evolutionary pressure is gone. Thus, the potential for a vaccine to drive the propagation of a more virulent strain if all other things are equal. However, there's good reason to believe that all other things will rarely be equal. The survival rate of the host is just one selection pressure. Anything can be a selection pressure if it has an impact on reproductive success of a subset of the population. It's possible that increased host survival is a very tiny or even zero pressure - for example, if the virus has a long contagious period, it might have already done all the spreading it's going to do before onset of symptoms and death, rendering survival time irrelevant. Other pressures could dominate - for example, the virus could be susceptible to being killed by sunlight, favoring variants with a light-insensitivity property over variants with a virulence property. One could even imagine how host symptoms could create positive pressure towards virulence - for example, more coughing and bleeding could help transmission. Such a virus would have its survival chances reduced by a leaky-but-symptom-reducing vaccine, and increased by vaccine-avoidance. Evolution is spectacularly multi-dimensional. None of these outcomes are inevitable.
- Izkata 5y ago
  That was an especially frustrating period. The vaccine trials never tested for that, and later studies were all like "maybe it does", so the sars-cov-2 vaccines preventing infection was always misinformation and no one was willing to accept that. At least people are aware of it now I guess?

edmundsauto 5y ago

> I sincerely hope the people who devised this vaccine know what they are doing. I think we all hope this. I can say that I sincerely believe the people who devised the vaccine know a hell of a lot more than just about anyone else on the planet. I don't trust experts in economics or socio-politics, but I do trust experts in virology. Not to say their information is perfect, but they know so much more than other people in a field where expertise is connected to outcomes.

cloutchaser 5y ago
The people who said vaccines will prevent infection and spreading of Covid?
- edmundsauto 5y ago
  Nuance matters here. Vaccines do prevent the spread, it's just not 100%. Are you a Bayesian? If so, using the prior of "vaccines are pretty effective at preventing spread" was reasonable until new data came in - this was a brand new technique in a novel virus. Further, the environment changed due to mutations - the fair question is "how effective was the vaccine at preventing the spread of the origin virus?"

reducesuffering 5y ago

Man, I regret reading this. The cynic in me immediately jumps to a possible world is where a pharmaceutical company is incentivized to bring about a world where every human needs a Medicine-as-a-Service to not die. The world's greatest $ printer.

cloutchaser 5y ago
To be fair they already have this with polio, mumps, rubella and others.