Vaccines work by prompting your immune system to recognize, and learn how to properly deal with, a virus or bacteria of a certain type. In this manner, vaccines provide protection against an antagonist, a shield to keep your body safe from the damages of pathogens.
After so many years of dealing with creationists and their ilk, I've come to notice that the way they act is similar to the way vaccines work. Religion seems to put up an impregnable barrier around their minds that keeps out science, facts, and rational thoughts. Religion acts just like a vaccine, except it works on the mind to keep out facts rather than on the body to keep out pathogens. This has lead me to coin a new term: Religion acts as a factcine on the mind. Creationists have been factcinated against critical thinking.
This applies to other groups too: astrologers, new age practitioners, 9/11 truthers, the entire Green Vaccine movement, psychics and their supporters - they all have been factcinated in one form or another to ignore the facts. And, just like a vaccine teaches your body how to fight off a pathogen, so does factcination teach these people to actively fight away facts. Factcination is dangerous: not because factcines contain dangerous chemicals like vaccines supposedly do (they don't) but because they contain even more dangerous stuff: vile lies and ignorance.