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?
As for Sweden, there's a lot of variety in human behavior and a lot we don't understand about the virus, and there are many possible explanations for the lack of major spread in any particular area. Sweden has continued to post a steady low level of cases over the last two months, not a continuing bell-curve decline, suggesting the virus is still consistently finding new hosts, just at a low and steady pace.
As for Sweden, there's a lot of variety in human behavior and a lot we don't understand about the virus, and there are many possible explanations for the lack of major spread in any particular area. Sweden has continued to post a steady low level of cases over the last two months, not a continuing bell-curve decline, suggesting the virus is still consistently finding new hosts, just at a low and steady pace.
[0] https://www.reuters.com/article/us-health-coronavirus-spain-...
[1] https://www.theguardian.com/world/2020/may/21/just-7-per-cen...
[2] https://medicalxpress.com/news/2020-09-doctors-hard-hit-madr...