CDC says 0.26%.
... so that's 894,000 infected in a country of 10 million, or 8.84% who've been infected.
Using 0.26%, I get 2,235,000 million Swedes who were infected, or 22.35% of the population. Using the herd immunity theory that includes T cell immunity, 22.35% is a pretty high infection rate number herd immunity.
When a population achieves herd immunity, new case transmission reduces quickly towards zero because the virus can no longer find vulnerable hosts to infect. Sweden continues to see a steady flow of new cases.
The number of cases depends on the number of tests and other factors. Looking at deaths, I see Sweden and NYS as example where death are very close to zero.