The Delta variant is contagious enough that we'll never achieve a level of herd immunity sufficient to protect unvaccinated people. All of us will be infected eventually, it's basically inevitable. Fortunately the vaccines are very effective at preventing deaths.
https://www.businessinsider.com/delta-variant-made-herd-immu...
They are less likely to be infected, and it looks like they have a shorter infectious period.
Herd immunity may be achievable with this in mind, but no one really knows right now. New variants may change the calculus too.