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

Mercado VJ., Contreras DL., Wongnak P., Yamin FY., Chatchen S., Ngamprasertchai T., Pan-Ngum W.

BackgroundDespite 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.MethodsIn 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.FindingsAcross 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.InterpretationASEAN 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.

More information Original publication

DOI

10.1016/j.jiph.2026.103238

Type

Journal article

Publication Date

2026-04-01T00:00:00+00:00

Volume

19

Addresses

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