But to say they've reached herd immunity is clearly wrong. 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. What they've managed to do is slow and control the spread.
Further, if you look at their total deaths so far (5,810), you can work backwards to see their total likely case counts. The current best estimate infection fatality rate (IFR) for COVID-19 is 0.65%, so that's 894,000 infected in a country of 10 million, or 8.84% who've been infected. Run the same numbers for Louisiana, you get 4,687 deaths and 721,000 infected from a population of 4.65 million for an infected rate of 15.5%. For New York it's 32,937 deaths, 5.1 million infected, population of 19.5 million, or 26% infected. New Jersey has 28% infected. All three are seeing new cases and new deaths.
So do I think that Sweden, with 8.84% of its population having been infected, is anywhere near herd immunity when 28% of New Jersey has been infected and more cases keep coming in? No, I don't. But none of it's going to matter when we have vaccines soon.
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.