Herd immunity is 70%. This is a longstanding thing that has always been known. " Experts estimate that in the U.S., 70% of the population — more than 200 million people — would have to recover from COVID-19 to halt the epidemic."
Mayo Clinic Herd Immunity
Anyways, even that, it doesn't even mean you need 200 million people vaccinated, just 200 million people immune which can come from getting the virus. Some still have really strong antibodies after 10 months, some begin to slowly dissipate after 3 months.
Lastly, we are not talking about having herd immunity, we are talking about the stadiums reopening. We do not need to wait until we get to that point before we reopen stadiums. What we need to have happen is getting our elderly vaccinated and thereby our deaths drop and thereby our hospitals free up. Once that death rate drops down to the levels we are seeing with the youth due to the severe patients being immune, we will have our country re-opening. Again, its not a return to normalcy as masks and other measures will still be in place but I have little to no doubt the stadiums will be back open again this fall.
Don't take my advice, take Fauci's.....
Fall Sports Stadium Attendance