Herd immunity happens long before we are all infected. Less than 40% of the US population is completely unvaccinated, which means we can open up more without overwhelming hospitals. That does put the unvaccinated at increased risks, but the general public is seemingly unwilling to continue lockdowns to protect people choosing not to be vaccinated.
If ~85% is needed for herd immunity then we could be rapidly approaching that point. Though specific locations would likely have outbreaks even if it was less of a concern nationally.
With an R0 of about 6 for the Delta variant, herd immunity won't provide a meaningful level of protection for most people. Herd immunity works with less contagious diseases because susceptible individuals can go their whole lives without exposure. But with SARS-CoV-2 now being endemic worldwide we'll all eventually get exposed, it's just a question of when. So the smart move is for everyone to protect themselves by getting vaccinated and actively treating co-morbid conditions like obesity, diabetes, hypertension, and hypovitaminosis D.
Any further lockdowns at this point cause far more harm than benefit.
They can prevent hospitals from being overwhelmed. Opening or not opening schools are one case where local communities are going to adjust based on the rates of hospitalization.
There's math you can do to roughly judge impact of partial vaccination. If R0 is six, and you're looking at hospitalization, estimate vaccine efficacy for Delta at around 90% (I've seen estimates above and below that).
Taking your estimate of a 60% vaccination rate:
6 * (1 - (.6 * .9)) = 2.76
2.76 is the effective Rt, which is far above 1, so no, that is not enough to open up more without eventually overwhelming hospitals.
Natural immunity from catching COVID, and other (inherently temporary) mitigation measures like masks/distancing/lockdowns would bring that Rt down further. But clearly what is best is more vaccination.
2.76 assumes normal conditions, social distancing literally changes the equation.
Mask use for example pushes that down. It’s easier to get below 1 with a 50% vaccination rate than a 0% rate. Meaning we can open up more without overwhelming hospitals.
That's pretty much what I said in my last line. The problem is, "opening up more" generally tends to mean things like less masking and less social distancing. So to the extent that Rt is pushed down by mitigation measures, Rt gets pushed back up when those mitigation measures end.
The advantage in my mind is you can avoid the most costly mitigation strategies.
Unfortunately, vaccination rates are age dependent so opening schools is a very high risk activity. Children are at low risk for COVID but they would be a major vector for transmission as everyone under 12 is unvaccinated.
That’s quite regional. Nationwide there is still plenty of ICU beds available, and presumably if it gets bad enough hot spots will respond appropriately.
By moving people with covid to other states, or importing medical personnel and equipment. Do so aggressively enough and you can keep capacity available.
And then you'll eventually realize: having thousands of people getting intensive care at the same time until everyone either had it or died from it is moraly not acceptable. Why do you come up with the idea that it's better to increase capacity rather than using large scale vaccination efforts?
If ~85% is needed for herd immunity then we could be rapidly approaching that point. Though specific locations would likely have outbreaks even if it was less of a concern nationally.