Apologies for being morbid, but that's what we call a self-fixing problem, isn't it? On a Darwinistic level, people either adopt an effective threat assessment approach or they die.
EDIT: Following up on some of the comments, note that I didn't actually say whether vaccine deniers do or do not have an effective threat assessment approach - I don't know. While I personally do believe in the effectiveness of vaccines, I definitely am not qualified to be making risk decisions for other people, and it's important for me to say this, because I don't want other people to make decisions for me. For example, I don't want others to tell me to not do extreme sports, or not to go out to the wilderness, or not to drink alcohol, etc, regardless of whether society feels that this increases my health risks. I strongly believe that a core part of being free is being able to make these decisions for oneself. I agree that we should have some way of preventing harm to others, but it can't be something that comes at the cost of removing people's bodily autonomy (or even just denigrating people for choosing differently).