In SIR models you can overshoot herd immunity, right? As such, I’m not sure I should take ~30% seroprevalence as strong evidence that herd immunity is greater than ~20%. That being said, it’s hard to understand how you could have ~70% seroprevalence if herd immunity is ~20%.
To be clear, I think the 71% result needs more investigation and (on priors) is probably lower. Yes, there is reason to expect overshoot. It seems the amount of overshoot would vary based on (a) NPIs being taken at the time (e.g. are some people never leaving the house) and (b) proportion of people who have cross-immunity or innate reduced susceptibility. (In principle, you could imagine 80% of people in a town live as normal and 20% won’t leave the house till the pandemic is over.) Again, I think if we did a lot of studies, we’d get a sense of both the minimum herd immunity threshold and the variability in overshoot.
In SIR models you can overshoot herd immunity, right? As such, I’m not sure I should take ~30% seroprevalence as strong evidence that herd immunity is greater than ~20%. That being said, it’s hard to understand how you could have ~70% seroprevalence if herd immunity is ~20%.
To be clear, I think the 71% result needs more investigation and (on priors) is probably lower. Yes, there is reason to expect overshoot. It seems the amount of overshoot would vary based on (a) NPIs being taken at the time (e.g. are some people never leaving the house) and (b) proportion of people who have cross-immunity or innate reduced susceptibility. (In principle, you could imagine 80% of people in a town live as normal and 20% won’t leave the house till the pandemic is over.) Again, I think if we did a lot of studies, we’d get a sense of both the minimum herd immunity threshold and the variability in overshoot.