Abstract
Background: Despite global elimination goals, measles remains a persistent regional health challenge in the Association of Southeast Asian Nations (ASEAN). This systematic review and meta-analysis characterized the distribution of cases and deaths during ASEAN measles outbreaks (2015-2025) and computed pooled proportions of cases stratified by age, vaccination history, migration status, and indigenous group membership. Method(s): In this systematic review and meta-analysis (PROSPERO CRD420251149627), we searched Scopus, Medline, Embase, and Google Scholar through January 15, 2026, for studies on measles outbreaks in ASEAN (2015-2025) that stratified cases by age, vaccination history, or marginalized groups. A modified Joanna Briggs Institute/ROBINS-E tool was used to assess the risk of bias. Pooled proportions were calculated using random-effects generalized linear mixed models (GLMM). Heterogeneity and small-study effects were evaluated using I2 statistics and Luis Furuya-Kanamori (LFK) indices, respectively. Finding(s): Across 11 studies (15,679 cases), measles disproportionately affected children under five (n=10,867). Vaccination history reporting was near-complete in children but negligible in adults (0.22%, 95% CI: 0.00-73.41%). Among cases with known history, 73.20% (95% CI: 59.37-83.61%) were unvaccinated. Age-ineligible infants (<9 months) comprised half the unvaccinated burden (49.98%, 95% CI: 24.85-75.13%). Among vaccinated cases, 74.84% (95% CI: 44.48-91.70%) were not fully vaccinated. Significant heterogeneity was observed throughout (I2 >= 89.0%). Risk of bias was generally low. Transmission was also documented among migrant and indigenous subpopulations. Interpretation(s): ASEAN measles outbreaks are driven by immunity gaps in unvaccinated children, partially vaccinated individuals, and age-ineligible infants. Achieving and sustaining regional measles elimination requires closing coverage gaps and addressing systemic drop-outs between doses. Future strategies must prioritize lifecycle immunity, including enforcement of the 2nd dose of measles containing vaccine (MCV2) and potential adult boosters, digitized vaccine registries, and cross-border collaboration.Copyright © 2026 The Author(s). Published by Elsevier Ltd on behalf of King Saud Bin Abdulaziz University for Health Sciences. This is an open access article under the CC BY license.
