When outbreaks of vaccine-preventable diseases such as measles occur despite highly effective vaccines being available, it's easy to conclude that parents who don't vaccinate their children are misguided, selfish or have fallen prey to misinformation.As professors with expertise in vaccine policy and health economics, we argue that the decision not to vaccinate isn't simply about misinformation or hesitancy.In our view, it involves game theory, a mathematical framework that helps explain how reasonable people can make choices that collectively lead to outcomes that endanger them.Game theory reveals that vaccine hesitancy is not a moral failure, but simply the predictable outcome of...