This article takes up a game-theoretic perspective on California’s recently passed bill (SB 277) that closes all nonmedical exemptions for school-mandated vaccination. Such a perspective characterizes parental decisions to vaccinate their children as a collective action problem and reveals the presence of an incentive to free ride—to enjoy the benefits of others’ efforts to vaccinate their children without vaccinating one’s own. This article defends California’s legislation as a reasonable means of overcoming the free rider problem and of ensuring that the burdens of vaccination are shared equally.
