> Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and n

> Counterpoint is Madrid, Spain, which had one of the worst outbreaks in the spring (antibody tests showed prevalence of 11%[0], higher than Stockholm[1]) and now is having a severe outbreak again[2]. What explanation is there other than herd immunity not having been reached? The outbreak in Spain isn't as severe as you might think, there's a lot more positive tests, yet a lot less illness. Herd immunity just means that R=1 without precautions. I would agree that Spain hasn't quite achieved herd immunity, but spread right now isn't anything like earlier this year. One could speculate that because Spain went into such a strict lockdown, herd immunity could not be achieved, or that herd immunity was achieved, it just didn't last because COVID immunity doesn't last.