Vaccine Coverage at 36 Months and 7 Years by Parental Birth Country, Washington State.

BACKGROUND AND OBJECTIVES: Ensuring equitable vaccination access for immigrant communities is critical for guiding efforts to redress health disparities, but vaccine coverage data are limited. We evaluated childhood vaccination coverage by parental birth country (PBC) through the linkage of Washington State Immunization Information System data and birth records. METHODS: We conducted a retrospective cohort evaluation of children born in Washington from January 1, 2006 to November 12, 2019. We assessed up-to-date vaccination coverage status for measles, mumps, and rubella (MMR), diphtheria, tetanus, and pertussis (DTaP), and poliovirus vaccines at ages 36 months and 7 years. Children with ≥1 parent(s) born in selected non-US countries were compared with children with 2 US-born parents, using Poisson regression models to provide prevalence ratios. RESULTS: We identified 902 909 eligible children, of which 24% had ≥1 non-US-born parent(s). Vaccination coverage at 36 months by PBC ranged from 41.0% to 93.2% for ≥1 MMR doses and ≥3 poliovirus doses and 32.6% to 86.4% for ≥4 DTaP doses. Compared with children of US-born parents, the proportion of children up to date for all 3 vaccines was 3% to 16% higher among children of Filipino-, Indian-, and Mexican-born parents and 33% to 56% lower among children of Moldovan-, Russian-, and Ukrainian-born parents. Within-PBC coverage patterns were similar for all vaccines with some exceptions. Similar PBC-level differences were observed at 7 years of age. CONCLUSIONS: The linkage of public health data improved the characterization of community-level childhood immunization outcomes. The findings provide actionable information to understand community-level vaccination determinants and support interventions to enhance vaccine coverage.

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

Objectives. 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. Methods. 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. Results. 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%; P ≤ .001), and results were similar with Oregon as a control state (no change observed in Oregon; P = .68). MMR exemptions overall decreased 41% (from 3.1% in 2018-2019 to 1.8% in 2019-2020; P ≤ .001), and religious exemptions increased 367% (from 0.3% to 1.4%; P ≤ .001). Conclusions. 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. Public Health Implications. 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. (Am J Public Health. 2023;113(7):795-804. https://doi.org/10.2105/AJPH.2023.307285).