In early 2020 I had a flu-like illness (as the doctors say) for two weeks during which I tested negative (PCR) for COVID. About a week after the symptoms cleared, I started testing positive, again for about two weeks, but with no symptoms. This was long before vaccines.
A couple of months later I was tested for COVID antibodies and was positive. In late 2021, after two vaccinations, I tested positive a couple of times but with no symptoms at all. It seems to be a many-faced illness.