Irrational exuberance for the vaccine drives some people to doubt.

The vaccine is a very reasonable thing to get but that doesn’t mean everyone in favor of it is behaving or thinking rationally.

When you have people turning something reasonable into a quasi religious moral obligation it is going to attract opposition, behaving irrationally is harmful even for something which is a good idea.

Reverse psychology. I know lots of people who say something along the lines of, “if it worked they wouldn’t need to pay me to get it”

People are weird that way and will allow confirmation bias to push them even more out of whack