This study examines the effects of removing vaccine exemptions on the incidence of pertussis (whooping cough) in the United States, with a focus on policy changes in California (2015) and New York (2019). Using county-level data from five states (California, New York, Arizona, Minnesota, and Florida) between 2010 and 2022, we estimate the impact of religious and philosophical vaccine exemptions on pertussis incidence. Our findings suggest that both religious and philosophical exemptions are associated with notable increases in pertussis case incidence. We further identify that the impact of both religious and philosophical exemptions is substantially higher in counties experiencing very high transmission of the disease. Our results indicate that eliminating philosophical exemptions can be an effective public health strategy in controlling disease outbreaks, especially in areas with low vaccination coverage. Nonetheless, the overall effect of vaccine mandates on herd immunity does not appear to be limited to outbreaks. We recommend further research to explore the longitudinal impacts of vaccine policies and the role of exemption uptake rates in disease transmission.
Paper
This paper was published in the Spring 2025 edition of the Tulane Journal of Policy and Political Economy. To view the paper, please visit the journal’s website at www.tulanejournal.org.