Identifying clusters of high vaccination exemption rates among schools and their determinants

All U.S. states require vaccinations for school entry; Exemptions may be requested based on medical conditions or religious or philosophical/ personal beliefs. Parental misconceptions regarding vaccinations have led to an increase in personal belief exemptions (PBE). The decision not to vaccinate affects the individual child as well as the community at large. Characterization of PBE, including their spatial distribution, has not been well explored. Therefore, the primary aims of this research were (1) to characterize the Arizona schools with high rates of permanent PBE among kindergartners and (2) to determine to which degree they aggregate across the state. Data for permanent PBE rates were accessed through the 2010-2011 kindergarten Immunization Data Report (IDR) from the Arizona Department of Health Services, and were linked to the 2009-2010 data from the National Center of Education Statistics (NCES). Incidence rate ratios (IRR) were calculated using negative binomial regression and hotspots were identified using Getis-Ord Gi*. Overall 2050 of 75,788 kindergarteners (2.7%) had permanent PBE throughout 1,018 schools in Arizona, with some schools having PBE rates as high as 66%. Schools with highest proportion of white students compared to the lowest had the highest exemption rates (IRR of 14.11; 95% confidence interval [CI], 9.47-21.03). Statewide analysis of hotspots identified increased rates of permanent PBE in Northern Arizona as compared to other regions, while a more focused examination of Central Arizona region demonstrated a pattern of increased PBE from west to east. These results can inform public health entities of where to target prevention strategies for outbreaks of vaccine-preventable disease.