California had two measles outbreaks in the mid-2010s—including one that started at Disneyland. The outbreaks led many to say that California was suffering from a problem with vaccine skepticism. But that’s wrong. Look again at those elementary schools with 100 percent vaccination rates. It’s actually small pockets of people within the state—such as the parents who sent their children to a very specific brand of elementary school—who have a vaccine problem. John Wennberg would recognize the pattern in an instant. Vaccine skepticism is small-area variation.
