Quantifying the Polarization of Vaccine Policymaking Across State Legislatures

Objectives. To quantify partisan asymmetries in the introduction of legislation aimed at removing vaccine mandates, expanding exemptions, reducing funding for vaccines, and instituting other related policies ("antivaccine" policymaking). Methods. We developed and validated a protocol for manually content coding records of vaccine-related bill introductions across US state legislatures from 2019 to 2023 and descriptively assessed partisan asymmetries in bill introductions over time. Results. The volume of antivaccine bills introduced in state legislatures has been increasing steadily since the onset of the COVID-19 pandemic. Also, there have been strong partisan asymmetries in bill introductions, with 86% of antivaccine bills sponsored by lawmakers affiliated with the Republican Party. We found that the effects of bill sponsor partisanship are constant in multivariate models accounting for differences in legislative and gubernatorial party control. Finally, dozens of antivaccine bills have been signed into law. Conclusions. There has been strong partisan polarization in vaccine-related bill introductions in the aftermath of the COVID-19 pandemic. Public Health Implications. Growing partisan polarization may be responsible for recent increases in antivaccine legislative activity, which could in turn undermine vaccine coverage. (Am J Public Health. Published online ahead of print July 16, 2026:e1-e8. https://doi.org/10.2105/AJPH.2026.308535).