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I've also wondered about the end game and so far concluded that most societies (including the US) would go the vaccine route (which confers herd immunity) as op

I've also wondered about the end game and so far concluded that most societies (including the US) would go the vaccine route (which confers herd immunity) as opposed to natural immunity (what I think you mean by "herd immunity"), but I would love to hear what you think. The reason why I doubt the end game is herd immunity via natural infection is: * millions would die * health systems would get crushed * the virus is unlikely to disappear entirely, so would simmer around the world, triggering epidemics every few years or so. What do you think?

mlyle 6y ago
We may not have a choice, in that we're not guaranteed to have a useful vaccine in massive doses anytime soon. But rebutting your individual points: > millions would die Unlikely. Improved estimates (thanks to serological data) for infection fatality rate range from 0.3% to 0.5%. If we can protect the most vulnerable populations, we can have a lower death rate than this-- e.g. in the under-30 crowd, the risk of hospitalization is 1 in 500 and the risk of death a tiny fraction of this (1 in 5000 or less). Further, any variance of susceptibility or contact density means you don't need to reach 60% for herd immunity. Some estimates say that the real threshold may likely be 25% or less: e.g. https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v1?fbclid=IwAR3bdC5xcn6BuYkbwp13zCrRmCMa4i91WqJXszD6LgDDO9t2V0sowr02ZOI https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v... Further, lighter weight social distancing measures can further reduce Rt and attain herd immunity at a lower percentage. If you assume we need 40%, and 0.25% IFR from protecting the most vulnerable-- you come up with 328k deaths. This is bad, but less bad than many alternatives. Note that the shorter lived the controls protecting the elderly and other vulnerable people, the more effectively we can protect them, too. > health systems would get crushed We'd not want to do what New York did, but let's look at it as an example. New York's health care system (barely) sustained the load. Now they're very possibly most of the way to herd immunity in NYC. Yes, we'd like to flatten the curve a bit from this and be better prepared. > the virus is unlikely to disappear entirely, so would simmer around the world, triggering epidemics every few years or so. The long term immunity question is interesting. Of course, vaccines could help improve this picture even if one ends up with disease-spread based herd immunity. My personal belief is that A) total antibody-based immunity will last a few years, based on our experience with SARS-CoV-1; B) partial antibody-based immunity will likely last longer than that; C) memory B cell / T cell based immunity is likely lifelong and makes any subsequent course of disease less severe. That is, I think it's likely that the current human coronaviruses that cause the common cold might very well cause a high death rate and be very transmissable if exposed to an immunologically naive population. Of course, your third point holds even more true when it comes to interim suppression and containment efforts while we isolate and wait for a vaccine. It's an even more intractable issue to try and maintain suppression when the vast majority of the population is still susceptible.
- ekidd 6y ago
  > Unlikely. Improved estimates (thanks to serological data) for infection fatality rate range from 0.3% to 0.5%. This seems optimistic. I did the math last week, and 0.2% of New York City had died either from the coronavirus, or from something that was probably the coronavirus. About 21% percent of New York City was testing positive for antibodies. (Both deaths and antibodies are lagging indicators of infection, although a noticeable fraction of the deaths lag by quite a bit.) That would give us an IFR around 1%. If we needed to have two-thirds of Americans catch the virus to reach herd immunity, that would be about 2 million dead. With any luck, some people are already immune. And as you point out, variation in susceptibility may stop things earlier than that. The are some nasty side-effects in some percentage of survivors: Impaired breathing and damage from blood clots seem to be two of the most frequently mentioned, and Wuhan is apparently seeing a spike in dialysis patients. The CDC is predicting 3,000 deaths/day in the US by June 1st. This seems plausible: We'd only need a few other metro areas to have a NYC-style spike. So far, several countries do seem to be able to control the virus. But at this point, I increasingly fear that the US will not be able to do the same. We don't seem to be able to ramp up testing, and we haven't gotten the infection rate down to the point where contact tracing would work. And significant portions of the US seem to be giving up on control and going for a herd immunity strategy.
  - mlyle 6y ago
    > About 21% percent of New York City was testing positive for antibodies. From samples returned 10 days ago, so add a bit more lag. It's not beyond the realm of possibility that New York City has reached the herd immunity threshold. The biggest estimates of variance in contact networks and susceptibility (from fitting to case count data) predict a herd immunity threshold of ~15%. (Cited above). > We don't seem to be able to ramp up testing Testing, shmesting. It only provides a minimal adjustment to Rt; sensitivity isn't great, and you can't test everyone every day. > we haven't gotten the infection rate down to the point where contact tracing would work Nor will we. The most aggressive lockdowns produce case count decays of 40% or so per week-- possibly less. The suggested threshold for where contact tracing can work well is 1 infection per million population. The SF Bay Area probably has about 3500x that. -ln(3500)/ln(0.6) =~ 16 weeks. IHME was predicting the virus would magically go away in California with continued shelter in place in the next 3 weeks. They just backed away from this crazy prediction that the data has never fit. However, policymakers depended upon it in making the tradeoff: aggressive policies aimed at control could be justified if they'd really get us to a sustainable containment regime in a couple months. > And significant portions of the US seem to be giving up on control and going for a herd immunity strategy. In the end, the only long term paths are to radically change our way of life forever, or herd immunity. There's only really one vaccine effort that could deliver tens of millions of doses to North America by mid-2021, and that's the Johnson & Johnson program. Odds of that program's success are 50-50 at best.
rpiguy 6y ago
I do think a vaccine will be made available and likely sooner than anyone is predicting, but it will not be mandatory and if states or employers try to make it mandatory they will held up in lawsuits for years. I could see a future where, like the flu vaccine, everyone is encouraged to get a SARS COV2 vaccine and there will be reasonable compliance. Hospital systems were only really crushed in there places, Lombardi, NYC, and Spain. Only in Lombardi Italy did hospitals actually run out of beds (go over capacity). Even in London today the hospitals are under capacity. I am not saying this is a good yard stick to go by, I am pointing out that outside of three locations most hospitals are sitting virtually empty. Therefore it is unlikely health systems would be crushed. As far as millions would die, again I would say look to the mortality rates outside of the three outlier areas (Lombardi, Spain, and NYC) and the mortality is far below 1%. I can see a future where COVID kills as many people as the flu. I don't see a future with a crushing mortality rate. Viruses rarely disappear entirely, but the mortality rate is not high enough to be so afraid of it. It spreads fast, but not as fast as measles, whooping cough, or TB, which spread faster, kill more people, and also kill children. We try to eradicate those diseases for a reason. Covid is nowhere near their level. If we set the bar this low, we will be stopping the world economy every decade to fight viruses that bubble up and kill comparatively few people.

mlyle 6y ago

We may not have a choice, in that we're not guaranteed to have a useful vaccine in massive doses anytime soon. But rebutting your individual points: > millions would die Unlikely. Improved estimates (thanks to serological data) for infection fatality rate range from 0.3% to 0.5%. If we can protect the most vulnerable populations, we can have a lower death rate than this-- e.g. in the under-30 crowd, the risk of hospitalization is 1 in 500 and the risk of death a tiny fraction of this (1 in 5000 or less). Further, any variance of susceptibility or contact density means you don't need to reach 60% for herd immunity. Some estimates say that the real threshold may likely be 25% or less: e.g. https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v1?fbclid=IwAR3bdC5xcn6BuYkbwp13zCrRmCMa4i91WqJXszD6LgDDO9t2V0sowr02ZOI https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v... Further, lighter weight social distancing measures can further reduce Rt and attain herd immunity at a lower percentage. If you assume we need 40%, and 0.25% IFR from protecting the most vulnerable-- you come up with 328k deaths. This is bad, but less bad than many alternatives. Note that the shorter lived the controls protecting the elderly and other vulnerable people, the more effectively we can protect them, too. > health systems would get crushed We'd not want to do what New York did, but let's look at it as an example. New York's health care system (barely) sustained the load. Now they're very possibly most of the way to herd immunity in NYC. Yes, we'd like to flatten the curve a bit from this and be better prepared. > the virus is unlikely to disappear entirely, so would simmer around the world, triggering epidemics every few years or so. The long term immunity question is interesting. Of course, vaccines could help improve this picture even if one ends up with disease-spread based herd immunity. My personal belief is that A) total antibody-based immunity will last a few years, based on our experience with SARS-CoV-1; B) partial antibody-based immunity will likely last longer than that; C) memory B cell / T cell based immunity is likely lifelong and makes any subsequent course of disease less severe. That is, I think it's likely that the current human coronaviruses that cause the common cold might very well cause a high death rate and be very transmissable if exposed to an immunologically naive population. Of course, your third point holds even more true when it comes to interim suppression and containment efforts while we isolate and wait for a vaccine. It's an even more intractable issue to try and maintain suppression when the vast majority of the population is still susceptible.

ekidd 6y ago
> Unlikely. Improved estimates (thanks to serological data) for infection fatality rate range from 0.3% to 0.5%. This seems optimistic. I did the math last week, and 0.2% of New York City had died either from the coronavirus, or from something that was probably the coronavirus. About 21% percent of New York City was testing positive for antibodies. (Both deaths and antibodies are lagging indicators of infection, although a noticeable fraction of the deaths lag by quite a bit.) That would give us an IFR around 1%. If we needed to have two-thirds of Americans catch the virus to reach herd immunity, that would be about 2 million dead. With any luck, some people are already immune. And as you point out, variation in susceptibility may stop things earlier than that. The are some nasty side-effects in some percentage of survivors: Impaired breathing and damage from blood clots seem to be two of the most frequently mentioned, and Wuhan is apparently seeing a spike in dialysis patients. The CDC is predicting 3,000 deaths/day in the US by June 1st. This seems plausible: We'd only need a few other metro areas to have a NYC-style spike. So far, several countries do seem to be able to control the virus. But at this point, I increasingly fear that the US will not be able to do the same. We don't seem to be able to ramp up testing, and we haven't gotten the infection rate down to the point where contact tracing would work. And significant portions of the US seem to be giving up on control and going for a herd immunity strategy.
- mlyle 6y ago
  > About 21% percent of New York City was testing positive for antibodies. From samples returned 10 days ago, so add a bit more lag. It's not beyond the realm of possibility that New York City has reached the herd immunity threshold. The biggest estimates of variance in contact networks and susceptibility (from fitting to case count data) predict a herd immunity threshold of ~15%. (Cited above). > We don't seem to be able to ramp up testing Testing, shmesting. It only provides a minimal adjustment to Rt; sensitivity isn't great, and you can't test everyone every day. > we haven't gotten the infection rate down to the point where contact tracing would work Nor will we. The most aggressive lockdowns produce case count decays of 40% or so per week-- possibly less. The suggested threshold for where contact tracing can work well is 1 infection per million population. The SF Bay Area probably has about 3500x that. -ln(3500)/ln(0.6) =~ 16 weeks. IHME was predicting the virus would magically go away in California with continued shelter in place in the next 3 weeks. They just backed away from this crazy prediction that the data has never fit. However, policymakers depended upon it in making the tradeoff: aggressive policies aimed at control could be justified if they'd really get us to a sustainable containment regime in a couple months. > And significant portions of the US seem to be giving up on control and going for a herd immunity strategy. In the end, the only long term paths are to radically change our way of life forever, or herd immunity. There's only really one vaccine effort that could deliver tens of millions of doses to North America by mid-2021, and that's the Johnson & Johnson program. Odds of that program's success are 50-50 at best.

rpiguy 6y ago

I do think a vaccine will be made available and likely sooner than anyone is predicting, but it will not be mandatory and if states or employers try to make it mandatory they will held up in lawsuits for years. I could see a future where, like the flu vaccine, everyone is encouraged to get a SARS COV2 vaccine and there will be reasonable compliance. Hospital systems were only really crushed in there places, Lombardi, NYC, and Spain. Only in Lombardi Italy did hospitals actually run out of beds (go over capacity). Even in London today the hospitals are under capacity. I am not saying this is a good yard stick to go by, I am pointing out that outside of three locations most hospitals are sitting virtually empty. Therefore it is unlikely health systems would be crushed. As far as millions would die, again I would say look to the mortality rates outside of the three outlier areas (Lombardi, Spain, and NYC) and the mortality is far below 1%. I can see a future where COVID kills as many people as the flu. I don't see a future with a crushing mortality rate. Viruses rarely disappear entirely, but the mortality rate is not high enough to be so afraid of it. It spreads fast, but not as fast as measles, whooping cough, or TB, which spread faster, kill more people, and also kill children. We try to eradicate those diseases for a reason. Covid is nowhere near their level. If we set the bar this low, we will be stopping the world economy every decade to fight viruses that bubble up and kill comparatively few people.