Don't people who've been infected count toward the herd immunity. That ~30% of Americans. I know there's some overlap but if we can get to 70% of people vaccinated I think we'd be really close, no?
Reinfection and new variants surviving in networks like this imply COVID will be around for a very long time.
First, the virus can only spread broadly with an R0 above 1. Even if some portion of the population is susceptible to reinfection (vaccinated or natural immunity), so far there's been little evidence that it's widespread. In a fully vaccinated population, the R0 will only reach above 1 if the virus is able to break through vaccines wholesale.
Second, the vaccines seem to be highly effective at preventing serious cases, hospitalizations, and deaths, even in reinfected individuals.
[0] https://bnonews.com/index.php/2020/08/covid-19-reinfection-t...