The roles of neighborhood composition and autism prevalence on vaccination exemption pockets: A population-wide study.

The number of children entering schools without mandated vaccinations has increased in high-income countries due to the rise of nonmedical exemptions from school vaccination requirements. Herd immunity is threatened when unvaccinated children are concentrated in spatial pockets. Despite the role of vaccine-autism controversy in the current wave of the anti-vaccine movement, we do not know if exemption clusters are associated with local autism rates; it is often assumed that these clusters are merely the result of sociodemographic composition. This study uses data on the number of students with a Personal Belief Exemption reported by schools from 1992 to 2014 and unique data on the locations of children with an autism diagnosis in California to study the correlates of large exemption pockets. Our spatial analysis shows that the prevalence of autism is not associated with the locations of large pockets of vaccination exemptions. Likewise, the spatial distributions of socioeconomic factors and proximity to health care resources have limited roles in explaining these large exemption pockets. Racial/ethnic composition, however, has strong associations with the locations of the large pockets. Our results suggest that community-level interventions are needed to maintain herd immunity as exemption pockets are not merely the result of population composition.