I've not seen any who understood that they were free riding. All of the ones I've encountered think that vaccines are not only harmful but also not very effective, if at all. They credit the disappearance of diseases like polio to other factors, like improvements in sanitation. They're not selfish, they're catastrophically misinformed and think that they're one of the few people who knows the truth, that vaccines are a fraud.

(I have more experience with these people than I'd like. I missed out on a bunch of childhood vaccinations because of it, and still know a bunch. I'm certain it's no coincidence that the same group of people also believes in chemtrails, UFOs, UFOs destroying chemtrails, and one I just saw yesterday, that root canals cause cancer.)