Immunization gaps and measles outbreaks in ASEAN (2015–2025): A systematic review and meta-analysis

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. METHODS: statistics and Luis Furuya-Kanamori (LFK) indices, respectively. FINDINGS: ≥ 89·0%). Risk of bias was generally low. Transmission was also documented among migrant and indigenous subpopulations. INTERPRETATION: 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.