It's helpful to use Spanish Flu as a proxy. It was almost completely overlooked by historians, mostly due to it coming on the heels of WWI, but look at what 1921 and beyond looked like. Back to normal. That's with the same social distancing and mask-wearing measures we see today. But no vaccine.

What's clear is society now seems to be willing to let COVID run its course (and kill discriminately) as long as we keep below hospital capacity. If we allow that to happen, then we'll reach herd immunity, regardless of vaccine availability, within a couple of years.

Let's just hope it doesn't mutate.