Amanda is right about the threat posed by parents who refuse to vaccinate their children, as demonstrated by the recent outbreak of measles following the Super Bowl. The threat these parents pose is indeed to their very own children, for those who aren’t vaccinated are much more likely to contract measles if exposed. (In the Super Bowl case, at least 13 of the 14 people who’ve contracted the disease said they had not been vaccinated.) But it’s worse than that. It’s not just that, as Amanda rightly points out, “anti-vaccination parents are making a virtue out of selfishness, imagining that they’re doing right by their kid by making them a free rider that uses herd immunity.” It’s also that people who aren’t vaccinated pose a threat to everybody, including those of us who are vaccinated. It’s bad enough to make your child the guinea pig for your crackpot theories, but something altogether more sinister to put my child in harm’s way because of it.

Vaccinated children are threatened because, according to the CDC, childhood vaccines are effective for most, but not all, of those who receive them. For about 5 to 15 percent of us, the vaccine won’t cause us to develop immunity. And we might not find that out till we’ve contracted the disease. There are also babies too young to be immunized, and seriously ill people, such as those with leukemia, who can’t be. In California in 2010, nine infants too young to be vaccinated died during an outbreak of whooping cough. In other words, when you vaccinate your child, you’re not just doing it for her, or for the sake of other children whose parents might not vaccinate them. You’re doing it for every one of us.

