UC Riverside Undergraduate Research Journal

Measles cases are increasing in the U.S., raising concern about gaps in adult measles, mumps, and rubella (MMR) vaccination, which is poorly captured by current surveillance. Emergency departments (EDs) act as safety nets for underserved populations and can help identify gaps in adult MMR uptake. We assessed adult MMR up-to-date status, knowledge, and willingness to receive vaccination in the ED, nationally. We conducted a cross-sectional survey of adults aged 18–64 at ten U.S. EDs from April–December 2024. Participants completed a structured survey assessing MMR knowledge, self-reported vaccination status, reasons for non-receipt, and willingness to receive MMR in the ED. Outcomes were summarized as proportions with 95% confidence intervals (CIs). Multivariable logistic regression identified factors associated with not being up to date and willingness to accept vaccination. Among 2,456 participants, 25.0% (95% CI 23.3–26.7%) had not heard of the MMR vaccine, and 44.0% (42.5–46.4%) were not up to date. Factors associated with being unvaccinated included male sex (OR 2.21 [1.84–2.66]), African American (non-Hispanic) race (OR 2.27 [1.75–2.96]), Hispanic ethnicity (OR 1.98 [1.49–2.62]), non-English speakers (OR 1.53 [1.12–2.09]), and lack of primary care access (OR 1.25 [1.01–1.58]). Among those not up to date, 36.5% (33.6–39.4%) were willing to receive MMR vaccine if offered in the ED. Substantial gaps in adult MMR vaccination persist, especially among underserved populations. ED-based strategies might support targeted vaccine education and delivery during periods of increased transmission.