Do Non-medical Exemptions Reduce Childhood Vaccination Rates?

In this study we explore the impact of changes in vaccine requirements exemptions for school entry on subsequent childhood immunization rates. School immunization mandates have been highly effective in achieving target vaccination rates in the U.S. However, all states allow some form of vaccination exemption. In general, these exemptions fall into two main categories: medical and non-medical exemptions. Medical exemptions are granted when a specific vaccine can be detrimental to an individual’s health. All states allow for the medical exemption. Non-medical exemptions allow individuals to refuse vaccination based on deeply held religious beliefs (religious exemption), or for philosophical or personal beliefs that preclude vaccination (often referred to as philosophical or personal belief exemptions). While offering non-medical exemptions preserves parents’ autonomy to make medical decisions for their children, misplaced fear over vaccine safety and side effects in recent years has given rise to anti-vaccination sentiment and increased utilization of non-medical exemptions.

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.