You really don't know much about this subject do you? Of course some people have immunity against this, it's just that we don't have reliable testing to determine who does and who doesn't. Furthermore we have no idea how many people had Covid and never knew about it. Several people in my family had it, one of my tenants, and none of them experienced much more than a headache for a few days. There were a lot of people like that especially at the beginning when this wasn't even a big deal. Get a headache, take an aspirin like I always have. Tired? Take a nap and you'll be fine.
In November of 2019, I started to come down with what I suspected as bronchitis. No big deal, I've had it before. If it gets worse, I'll go get some antibiotics. In less than two weeks the symptoms disappeared and I was fine. Was it bronchitis? I'll never know because I never went to the doctor. Before I got my vaccine, I contacted my Doctor at the Cleveland Clinic to see if I could get an antibody test first to see if I needed the shot. The Clinic told me they refuse to use them due to the inaccuracies.