It comes from seropositivity rates in blood samples.
much of that is from vaccination though right. SO IT ABSOLUTELY DOES NOT COUNT AS HAVING COVID. Vaccination <> Covid. And when an omicron vaccine comes if it does, it will not be "having had Omicron". Vaccination is not having had it, vaccination usually prevents precisely that. Or am I going to claim I had TB, yea I've had TB, measles, mumps and rubella, tetanus, maybe polio.

If I had more risks I would not hesitate to get a 4th shot now though.