So 0% of those with mild symptoms or those who otherwise didn’t get a PCR/CT test had a COVID infection and it was always something else?
Not sure I understand, but in general they reference against old samples pre Covid, so we know they weren't asymptomatic Covid carriers.
Testing would have some correlation to severity of symptoms, and if the severity of infection (the mythical viral load?) correlates to antibody levels, then maybe some (more than 1%) of the mildest infections end up testing negative for antibodies?
It's always possible hypothetically, but we do know close to 100% of known covid carriers develop antibodies.
Granted, the studies are depending on PCR or CT to diagnose infection, so you can always claim people have it and it goes completely under the radar, but it's extremely hard to believe they would develop immunity under such circumstances.
If you were infected, but it doesn't show up on PCR or CT, and doesn't create antibodies, did you really have it?