It is very positive in that we can be more confident that our assumptions are close to reality. 0.5%*330M still equals 1.65M deaths, or (very roughly) 5M ICU beds. Spread out over 52 weeks, that's a lot of ventilators and ICU beds and PPE, but it is a target. A very big juicy target that we can and should aim directly at, and HIT.
So having killed 1.6 million in the US alone and run ICU at 100% for a year, you’re just going to hope people remain immune and the virus doesn’t mutate having passed through billions of people worldwide?
The alternative being...? We know that covid-19 will likely mutate, just like other coronaviruses, H1N1 and its mutations are still around every year; are you suggesting we must remain in quarantine until we both create a vaccine for covid-19 and then every fall quarantine until we're able to develop a vaccine for that year's bout of viruses?
It's more or less epidemiologically impossible that you will see an attack rate of 100% (as you just assumed). Once attack rate reaches >40~60%, the reproduction number drops below 1 because there just aren't enough uninfected hosts.
It will probably be significantly higher than 60%, since COVID-19's R0 without lockdown seems to be pretty high. The CDC has estimated it at 5.7 [0]. Herd immunity threshold = 1 - 1/R0, so the threshold would be 82.4%.
That R0 assumes we are taking essentially no measures to stop the virus though, right? I don't no much about it but it seems like the R0 would drop significantly if we keep doing social distancing, expand testing, make people wear masks, etc.
