Vaccine exemption requirements and parental vaccine attitudes: an online experiment.

Increases in vaccine hesitancy and vaccine-preventable disease outbreaks have focused attention on state laws governing school-entry vaccine mandates and the allowable exemptions (medical and nonmedical) from those mandates. There is substantial variation in the type of exemptions available in each state, and states with more rigorous or burdensome exemption requirements generally have lower exemption rates. States have little evidence, however, about how vaccine-hesitant parents respond to different requirements. Despite recent efforts to formulate "model legislation" templates for states to follow, policy evidence about optimal exemption regimes is limited to observational studies in states that have changed exemption laws. We conducted two online experiments to explore how parental attitudes and intentions responded to different school-entry vaccine mandate exemption requirements. We randomly assigned online participants to one of four hypothetical vaccine exemption application scenarios: parental signature only, a checklist of vaccines for which an exemption is requested, a lengthy (10-30+ min) video-based vaccine education module, and a requirement to write a statement justifying the exemption. Among parents with high vaccine hesitancy, a required vaccine education module led to significant decreases in vaccine hesitancy, while checklist and justification requirements increased vaccine hesitancy slightly. Among parents with low vaccine hesitancy, we observed a potential backfire effect when parents were required to write a justification statement. Our findings warrant replication in a larger, fully-powered trial to accelerate knowledge about how parents across the vaccine hesitancy spectrum respond to exemption regimes.