Potential Effects of California’s New Vaccine Exemption Law on the Prevalence and Clustering of Exemptions

摘要

Exemptions from childhood immunizations required for school entry have continued to increase among California kindergartners, and exemptions show spatial clustering within the state. A 2014 change in California’s school-entry vaccine exemption law requires parents filing for an exemption to submit signed documents from a health care provider. However, the evidence presented here suggests that the policy change will probably not be sufficient to reverse the growing trend in vaccine refusals. State-mandated immunization requirements for school entry have been instrumental in achieving high immunization coverage rates and ensuring herd immunity against infectious disease outbreaks. 1 However, in most states parents can obtain a personal beliefs exemption (PBE) from school-entry requirements. 2 A growing trend of parental vaccine hesitancy has led to an increase in PBE rates, and such increases are associated with higher risks of disease outbreaks. 3 In California, for example, rates of PBEs among children entering kindergarten increased by 380% from 1996 to 2010 (from 0.5% to 2.3%). 4,5 In response to rising PBE rates, California passed Assembly Bill 2109 (AB2109) in September 2012. 6 California’s previous law allowed a parent to obtain a PBE by signing an affidavit stating that immunization is contrary to the parent’s beliefs. 7 This affidavit was preprinted on the California School Immunization Record, making exemptions readily accessible. Previous research demonstrates an association between easier state exemption procedures and higher exemption rates. 8,9 Authored by state assembly member and pediatrician Richard Pan, AB2109 requires parents filing an exemption to submit an attestation signed by a health care provider stating that they have been provided information about the risks and responsibilities of refusing vaccination and an attestation signed by parents indicating receipt of this information. 6 AB2109 went into effect in January 2014. It is not yet known whether this policy change will reverse or slow the trend of increasing PBE rates in California, although a similar regulatory change in Washington appears to have reduced PBEs. 10 Here we present the most recent data on PBEs in California and demonstrate continued spatial variation in PBE rates statewide. These data represent the last kindergarten cohort before AB2109 was passed, so they will provide a useful baseline as the new law takes effect. We also discuss the implications of spatial clustering for the potential effectiveness of AB2109.