Vaccines are not foolproof, especially in the roll out stage. People have different responses. Effective HIV meds took ~ 15 years to be developed. Covid vaccine about 1 year. No HIV vaccine exists as yet, decades after HIV became a problem in the States.
My wife and I were both Covid vaxed. She got a mild case, rested a couple of days and was fine. Even though we lived together, I didn't get Covid. Not sure how she got it. Some people, even though exposed to Hepatitis B fight it off and remain essentially immune to it. Others get it, have their liver destroyed and require a transplant.
As I said before, anti vaxxers, if they keep to themselves, in effective isolation, are not a problem. If they want to be part of society, get vaccinated, for the sake of others. This is not a moral issue. It's really not even a matter of conscience. A person who owned an animal that was known to be dangerous would be put to death if the animal killed someone. How much moreso anti-vaxxers who infect others.