Herd immunity may be reached with much lower levels of spread in a community, city or nation maybe even down to 43% or even to 10-20% from the 70% scientists originally suggested. Poorer and harder hit neighborhoods could do a lot better than richer neighborhoods that were isolated more. The NYC's, Italy's and Spain's that got hit hardest, would do the best. This new theory if true support's Sweden's methods who did it by political design. That also bodes well for a vaccine with let's say a 50% efficacy rate.
This argument reminds me of thinking about buying a boat. I was down at the boat show and I saw this great boat that was marked down from $70,000 to $43,000. I was pretty excited. Then I talked to this guy who said that since it was last years model it would soon be marked down to $10,000-$20,000. The problem was I only had $2000 in savings, and I was waiting to see if my uncle was really going to die and leave me something.
None of that is true of course, but think about the price of the boat being the immunity percentage for herd immunity, my savings as the current percentage of immunity, and my hoped for inheritance the vaccine. I think heard immunity is going to be dependent on a very effective vaccine. It just doesn't look like it is in the cards that we are going to be able to die our way to herd immunity, not even in Sweden.
To be clear, I don't know anything about boats or epidemiology, so I may be wrong.