The Covid vaccine does not have a live virus in it. The mRNA vaccine does not even have a dead virus in it. There is no infection going on.You think intentionally infecting yourself with Covid repeatedly is good for your health, Wally?
A vaccine does create an immune reaction, which does cost the body a little bit. It is nothing compared to how much an actual infection costs the body. I would not get vaccinated for Smallpox, because that is not a likely infection, but Covid and influenza are very likely infections, so getting vaccinated against them made a lot of sense.