[spfzero]

Certainly the case with the PCR test, because it is so sensitive. It can detect Covid fragments at such a low level that no symptoms would show and no adaptive immune response would arise. That's not enough Covid to generate memory and immunity.

You could be PCR tested positive, while experiencing a cold or flu (which you would now understandably think were Covid symptoms), but would not have immunity for a future, larger infection from Covid.

Though statistically unlikely, it's bound to happen sometimes.