[nradov]

You're missing a big part of the picture. It is well established that some patients infected with SARS-CoV-2 either never produce detectible levels of antibodies, or have them fade away quickly. In order to measure actual infection numbers we need to look beyond antibody seroprevalence, and factor in CD4+ and CD8+ T cell assays as well.

https://doi.org/10.1016/j.cell.2020.08.017

[jhpriestley]

90% of PCR-positive subjects in the ENE-COVID test, for example, did also have a positive antibody test. So actual infection numbers might be ~10% higher than the raw numbers from the antibody tests (and I believe that this is factored into the results reported by such studies). It doesn't change our big-picture understanding of the disease.