State Policy Removing the Personal Belief Exemption for Measles, Mumps, and Rubella (MMR) School Immunization Requirement, Washington State, 2014-2022.

Abstract

<b>Objectives.</b> To assess the impact of Washington State's 2019 Engrossed House Bill (EHB) 1638-which removed measles, mumps, and rubella (MMR) personal belief exemptions-on MMR vaccine series completion and exemption rates in K-12 students. <b>Methods.</b> We used interrupted time-series analyses to examine changes in MMR vaccine series completion rates before and after EHB 1638 was passed and the χ² test for differences in exemption rates. <b>Results.</b> EHB 1638 implementation was associated with a 5.4% relative increase in kindergarten MMR vaccine series completion rates (95% confidence interval = 3.8%, 7.1%; <i>P</i> ≤ .001), and results were similar with Oregon as a control state (no change observed in Oregon; <i>P</i> = .68). MMR exemptions overall decreased 41% (from 3.1% in 2018-2019 to 1.8% in 2019-2020; <i>P</i> ≤ .001), and religious exemptions increased 367% (from 0.3% to 1.4%; <i>P</i> ≤ .001). <b>Conclusions.</b> EHB 1638 was associated with an increase in MMR vaccine series completion rates and a decrease in any MMR exemption. However, effects were partially offset by an increase in religious exemption rates. <b>Public Health Implications.</b> Removal of personal belief exemptions for the MMR immunization requirement only may be an effective approach to increase MMR vaccine coverage rates statewide and among underimmunized communities. (<i>Am J Public Health</i>. 2023;113(7):795-804. https://doi.org/10.2105/AJPH.2023.307285).