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TL;DR: How did a vaccine with a reduction of hospitalizations by a factor of 20 (94%) take us from "shut everything down" to "cases no longer matter"? (Caveat:

by axby 5y ago

TL;DR: How did a vaccine with a reduction of hospitalizations by a factor of 20 (94%) take us from "shut everything down" to "cases no longer matter"? (Caveat: maybe for omicron it's even less severe?) Edit: specifically, from what I understand the healthcare system can't handle everyone being unvaccinated and getting the virus, it would be overwhelmed by hospitalizations. But with a 20 times reduction in hospitalizations, it can? Or was it expected that the vaccine would reduce transmission to the point where it wouldn't spread so much? This sounds reasonable, but aren't fully vaccinated people ending up in the hospital pretty regularly too [2]? Using the 94% effective figure from the early trials, say fully vaccinated people are 20 times less likely to be hospitalized. I don't know much about virology but I understand exponential growth. It looks like the cases are doubling every 2 weeks (edit: I guess this might even be a few days? See [0]). In a few months, almost everyone will get it. In the last two week period, won't half the population catch it? In that case, even with 100% vaccination, hospitalizations would still be 1/20 of half the maximum due to COVID. Right? That's something I've never understood about the pandemic. Is reducing hospitalizations by a factor of 20 enough that having everyone get the virus is no longer a concern? Or was it expected that the vaccines reduce transmission enough that everyone wouldn't get it anymore? Canada has like 75% [1] (edit: oops, originally I said 85% here, but I guess that's in people 12 years and older) or higher vaccination and is still seeing record case numbers everywhere. This isn't really an argument for or against kids in schools. I am just surprised that people are so quick to say "we have a vaccine so there's no need to worry about COVID in anyone vaccinated now". Certainly it seems like many health officials say something similar, so I must have missed something. (Or are they just trying to encourage everyone to get vaccinated? I know that many people don't really understand the details and would (erroneously) just say "it's not 100% effective so why bother") Sources: * "The spread of the Omicron variant of coronavirus appears to be doubling every two to three days" [0] * "The cumulative percent of people fully vaccinated with a COVID-19 vaccine in Canada was 76.83% as of January 1, 2022." [1] * "Fifty per cent of hospitalizations now, in Quebec, are due to people not having been vaccinated," [2] [0]: https://www.theguardian.com/world/2021/dec/08/omicron-covid-cases-doubling-every-two-to-three-days-in-uk-says-scientist https://www.theguardian.com/world/2021/dec/08/omicron-covid-... [1]: https://health-infobase.canada.ca/covid-19/vaccination-coverage/ https://health-infobase.canada.ca/covid-19/vaccination-cover... [2]: https://www.cbc.ca/news/politics/duclos-mandatory-vaccination-policies-on-way-1.6307398 https://www.cbc.ca/news/politics/duclos-mandatory-vaccinatio...

iggldiggl 5y ago
> I don't know much about virology but I understand exponential growth. It looks like the cases are doubling every 2 weeks (edit: I guess this might even be a few days? See [0]). In a few months, almost everyone will get it. In the last two week period, won't half the population catch it? In that case, even with 100% vaccination, hospitalizations would still be 1/20 of half the maximum due to COVID. Right? As people become infected and gain immunity (in reality not always perfectly and not necessarily until the end of times, but on average they'll definitively do, and right now we're only talking about a simplified thought model anyway), they drop out of the pool of people available for further infections and therefore slow down the growth rate. While still only a simplified approximation, logistic growth is therefore a better model than naive unchecked exponential growth, and the maximum case rate will be somewhat lower than "half the population gets infected in the last doubling step".
- axby 5y ago
  Thanks, I actually hadn't heard of a logistic growth curve before (it looks like something I somewhat remember from high school chemistry). Can you recommend anything to read about this that apply it to the pandemic? I guess I'm beyond my math skills here. Reading normal news articles, they warn of increasing cases, but I'd like to see some raw numbers. The report they refer to is too complicated for me to understand :( Specifically I'm wondering what the maximum number of cases in a short period is likely. I ask because I was shocked to hear that the number of ICU beds in a major city of 1M people in Canada was only a few hundred (or maybe that was total hospital beds? I can't remember). So it seems like you need to keep your "hospitalizations per population" number down to less than the ratio of "hospital beds per population". Certainly I was wrong in saying "everyone will get it" in a few months because of the logistic growth curve, but it looks like a significant portion of the population could still be infected within the same period, even if you remove the 6% (Canada) to 20% (USA) people who have already been infected? And even if everyone is fully vaccinated, can the number of them that end up in hospital come close to the total capacity? It seems like we're already getting close to capacity.
  - iggldiggl 5y ago

by axby 5y ago

iggldiggl 5y ago

> I don't know much about virology but I understand exponential growth. It looks like the cases are doubling every 2 weeks (edit: I guess this might even be a few days? See [0]). In a few months, almost everyone will get it. In the last two week period, won't half the population catch it? In that case, even with 100% vaccination, hospitalizations would still be 1/20 of half the maximum due to COVID. Right? As people become infected and gain immunity (in reality not always perfectly and not necessarily until the end of times, but on average they'll definitively do, and right now we're only talking about a simplified thought model anyway), they drop out of the pool of people available for further infections and therefore slow down the growth rate. While still only a simplified approximation, logistic growth is therefore a better model than naive unchecked exponential growth, and the maximum case rate will be somewhat lower than "half the population gets infected in the last doubling step".

axby 5y ago
Thanks, I actually hadn't heard of a logistic growth curve before (it looks like something I somewhat remember from high school chemistry). Can you recommend anything to read about this that apply it to the pandemic? I guess I'm beyond my math skills here. Reading normal news articles, they warn of increasing cases, but I'd like to see some raw numbers. The report they refer to is too complicated for me to understand :( Specifically I'm wondering what the maximum number of cases in a short period is likely. I ask because I was shocked to hear that the number of ICU beds in a major city of 1M people in Canada was only a few hundred (or maybe that was total hospital beds? I can't remember). So it seems like you need to keep your "hospitalizations per population" number down to less than the ratio of "hospital beds per population". Certainly I was wrong in saying "everyone will get it" in a few months because of the logistic growth curve, but it looks like a significant portion of the population could still be infected within the same period, even if you remove the 6% (Canada) to 20% (USA) people who have already been infected? And even if everyone is fully vaccinated, can the number of them that end up in hospital come close to the total capacity? It seems like we're already getting close to capacity.
- iggldiggl 5y ago