You really think that 50% of the population is the high end???
Per https://www.thelancet.com/journals/laninf/article/PIIS1473-3... it seems that the basic reproduction number is over 2. Which means that herd immunity only sets in if under 1/3 of the population is vulnerable. Which means over 200 million Americans get it.
The alternatives are permanent lifestyle changes, or a successful eradication of the disease worldwide.