That’s because the vaccine didn’t exist when I was a kid. I got the disease instead, leaving me with natural immunity. I think my chums all got it too and it amounted to a few days of discomfort, no big deal. But there must have been some who got it and suffered serious consequences, even death. News just didn’t get around in those days (ca. 1950) like it does today.

It’s terrific that a vaccine now exists, but like all vaccines it entails perverse incentives. When nearly everyone is vaccinated, there is little incentive for an individual parent to get it for his child because the disease can’t spread through a vaccinated population, and at least some incentive not to get it: cost, bother, and a remote chance of ill effects. And if enough parents skip the vaccine, the percentage of vaccinated children may fall low enough to permit…