>A bit under half of Americans have already caught covid
No- that many have had a positive test or other diagnosis confirming covid.
There were plenty of non-hospitalized, non-diagnosed cases before the tests existed. And plenty of people have had it and never saw a reason to get a test to confirm it.
So that's not quite true. The CDC provides the estimate you're talking about which is what my post originally cites (~146mm Americans infected). That's their estimate based on the much smaller number of positive tests and hospitalizations, using their models about how many cases are missed by surveillance.
makes me wonder if repeated exposure that doesn't result in the virus replicating enough to take hold in the body gives you any kind of immunity, or if that is even a possibility. like how many viral bodies does it take, just 1?
Even without vaccines, that means nearly half of Americans already have natural immunity which is vastly superior to vaccine immunity.
https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd...