Vaccines can bring the R number below 1 from above 1, which means that it really doesn't spread out of control anymore, and becomes much less common in the population.
That claim is an article of faith in some circles but there is actually no reliable scientific evidence that even a high level of vaccination can drive R0 below 1. Transmission will slow down as more people gain some level of immunity one way or another but the virus is now endemic and all of us can expect to get exposed occasionally. Fortunately the vaccines are still very effective at preventing deaths.
Thanks for mentioning R. For a bit of good news, current estimates are that most states/counties currently have R < 1, https://covidestim.org. Hopefully we've passed the worst of Delta. I have no doubt vaccines helped, though I'm unsure how much. Obviously we didn't needed 100% vax rate to get to this point. Comparing with the situation a month ago obviously something else other than vax (and/or masks) has had a big hand in the R reduction (hint, natural immunity).
What I am pointing at is that there is a population vaccination level beyond which further vaccination has diminishing returns. There are fundamental principles like bodily autonomy and human dignity that we shouldn't throw away just to chase a slightly lower R number, cumulative deaths with covid, or any hyperfocused metric we use to track the pandemic evolution.
PS. I hold the underlying assumption that covid is endemic and over the next decade we'll keep having outbreaks until everybody builds up sufficient natural immunity.
https://www.businessinsider.com/delta-variant-made-herd-immu...