You have to understand that taking your chances with vaccination, when adverse side effects are still very rare and usually treatable, is morally superior to [i]not[/i] doing so and risking infection by diseases that are much older, more stubborn, and more lethal. Sure, a child's immune system can respond well to most diseases naturally anyway. Would you bet their life on that, though? Herd immunity is an incredible phenomenon, but it wouldn't really exist if it weren't for our society's general disapproval of abstaining from vaccination.