Do Non-medical Exemptions Reduce Childhood Vaccination Rates?
Discussant: Jing Xu
While previous studies indicate that the availability of personal belief exemptions is associated with increased rates of non-medical exemptions, and increased outbreaks of vaccine preventable disease, it is unclear whether the availability of non-medical exemptions has a causal impact on immunization coverage for required childhood vaccines. Our study is the first that investigates the causal effect of non-medical exemptions on childhood vaccination rates. We use repeal of non-medical exemptions in California to construct a difference-in-differences framework.
In 2015 California experienced the most severe measles outbreaks in over a decade attributable to vaccine hesitancy. The outbreak started at Disneyland in Orange County, “a hotbed of the anti-immunization movement”, and ultimately infected 131 Californians. California quickly responded to the 2015 measles outbreak by repealing all non-medical exemptions within the year. We combine information on changes in states’ exemption provisions with county-level vaccine-specific rates for 5 childhood vaccination, and exemptions rates, from 2009-2017. We control for an extensive set of covariates and prevalence of vaccine preventable disease, as well as county and year fixed effects. We find that the repeal of non-medical exemptions is associated with an increase in 5 major childhood vaccinations. Non-medical exemption rates fall after the repeal; however, medical exemption increases in California relative to the control states.
Full Papers:
- exemption repeal and vaccination-ASHEcon.pdf (2038.1KB) - Full Paper