While I have, of course, zero hesitation about the utility and safety of vaccination, I could never quite understand why everyone made such a big deal of anti-vaxers — surely they were just putting their own health in jeopardy, so it’s their own business? (Well, and that of their kids, but, you know, kids, who cares, not I.) But:

Two of the Disneyland cases were too young to be vaccinated – the first dose is recommended at 12 months – so those parents never had the choice to protect their children from measles.

Okay, that’s a given, but, more importantly, here’s the part I was unaware of, even though it’s obvious as soon as you think about it:

No vaccine is 100% effective, however, and even the measles vaccine, with effectiveness approaching 100%, cannot prevent every person who receives it from catching the disease if they’re exposed. In a population where nearly everyone has been vaccinated except those who have medical reasons not to be, though, the disease can’t travel as far, so cases are contained before they turn into outbreak.