Herd Immunity
"Across the country, about 259.8 million doses have been administered. That translates to 78 doses per hundred people."
https://www.cnn.com/interactive/2021/health/us-covid-vaccinations/
Some of these are the double dose; assuming 50% of population (not 78%) vaxxed yields approx. 160,000,000.
Johns Hopkins is showing 32,700,000 positive test results.
https://coronavirus.jhu.edu/
Herd Immunity for COVID-19 is 60 -75%; 200 - 250 million.
The total of vaxxed plus known cases (from above) is just 7,000,000 shy of the lower bound. There could be easily that many undetected positives. If you use NBC's numbers (pic) 10 x 32.7 M = virtually the entire country.
Don't let anyone tell you "September".