They teach our bodies how to battle viruses and bacteria so that when a real attack comes, they can handle it without trouble. Anyone who’s got some basic idea of vaccines or biology knows this, so it’s incredibly worrying that there are so many people who don’t vaccinate their kids.
But don’t take it from me, listen to this guy. An immunologist came across a very anti-vaccine meme on Tumblr and completely and utterly eviscerated them.