Comment by birken

Your link (0) doesn't rebut the seroprevalence studies at all. It is talking about T-cells, which is not what the CDC seroprevalence studies are measuring. The CDC is testing for SARS-CoV-2 IgG antibodies in blood. And look, if the CDC's seroprevalence studies can't convince you, then I'm not going to. They have data on the specificity and sensitivity of their antibody tests, which gives high confidence ranges for the data. They talk about their methods in detail [1]. And these tests are not about calculating herd immunity, not about calculating who might have prior immunity from a related disease, not about saying who can or cannot get COVID again. They are merely tests for very specific antibodies that are formed in a high percentage of people who had COVID. Thus they should be very accurate at determining how many people have had COVID if the proper statistical care is taken in interpreting the results (which it is!).

With ~7M confirmed cases in the US, and your estimate of 10M cases, that would be a multiplier of less than 1.5x from confirmed cases to estimated cases. That is well below any of the seroprevalence estimates, and remember many of these cases happened months ago when there was almost no testing. The positive test percentage in NY was at or above 20% until May! It was over 40% for the first half of April! Also the current positive test rate in the US is ~5%. There still is a lack of testing in many places.

Also using the death rate alone in trying to figure out the number of cases is highly prone to error, since the virus has death rates that can vary by over 10,000x based on age (85+ vs <18) [2]. And this is especially true if many of the people who don't die, also don't even get seriously ill and thus don't get tested. Combining seroprevalence studies, hospitalizations and deaths by age group is a much more accurate method, and there is no way you could reasonably look at the data points and come up with 10M total estimated cases.

1: https://www.cdc.gov/mmwr/volumes/69/wr/mm6932a4.htm

2: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/investi...