Exposure to Personal Belief Exemptions from Mandated Vaccines among California Kindergarteners, 2008-2010

Alison M. Buttenheim, University of Pennsylvania
Malia Jones, University of California, Los Angeles

Personal belief exemptions (PBEs) from mandated school vaccinations have risen in California over the past decade. Disease outbreaks in the state are thought to be associated with clusters of intentionally unvaccinated children. However, no previous studies have quantified the clustering of PBEs within California schools. This study employs measures from the residential racial segregation literature to assess the extent of and trends in exposure of California kindergarteners to PBEs at school. Using data from the California Department of Public Health, we calculate exposure and isolation indices for the state and by county. Results indicate that more than 20,000 kindergarteners in California attend schools with epidemiologically worrisome rates of PBEs. Trends point to increased exposure over time, but not increased concentration of children with PBEs within schools. Schools with a high prevalence of intentionally unvaccinated children are epidemiologic “hotspots” and should be the focus of policy and programmatic interventions.