Measles outbreak risk in Afghanistan: provincial immunity gaps and epidemic potential following immunisation system disruption.

Publication date: Aug 25, 2026

Following the 2021 political transition, Afghanistan’s routine immunisation system experienced disruption. The 2022-23 Afghanistan Multiple Indicator Cluster Survey (MICS) estimated national first-dose measles-containing vaccine (MCV1) coverage at 51. 2% (95% CI 49. 1-53. 2). Provincial heterogeneity in coverage-derived measles transmission potential has not been quantified using these household survey data. Provincial MCV1 coverage among children aged 12-23 months was obtained from the 2022-23 MICS (unweighted n = 6177; weighted n = 6383). We calculated a coverage-adjusted transmission-potential index, R = R₀ cD7 (1 – MCV1 cD7 VE₁), using R₀ = 15 and one-dose vaccine effectiveness (VE₁) = 0. 93. Deterministic SEIR scenarios and complementary stochastic tau-leaping simulations were run using an 8-day mean latent period and 4-day infectious-compartment duration. Survey uncertainty, upper-bound routine-MCV1 protection gaps, and preferential- and random-targeting SIA requirements were quantified. Provincial MCV1 coverage ranged from 8. 6% to 88. 7%, and all 34 provinces had R > 1 (range 2. 63-13. 80; U5-weighted aggregate 7. 95). The theoretical one-dose coverage requirement was 100. 36%, whereas the requirement for a complete two-dose series using empirical VE₂ = 0. 97 was 96. 22%. The standardized 3. 5-year upper-bound accumulation of children remaining unprotected by routine MCV1 was 3. 02 million (conditional 95% interval 2. 92-3. 12 million). The province-summed SIA requirement was 4. 06 million children (49. 8% of U5) under idealized preferential targeting and 7. 53 million (92. 4%) under random targeting. Single-importation establishment probability ranged from 65. 9% to 93. 9% across nine illustrative provinces. WHO week-14 surveillance showed positive ordinal geographic concordance with R (Kendall τb = 0. 331; Spearman ρ = 0. 430; both p = 0. 011). Routine MCV1 alone is mathematically insufficient to reach the population-immunity threshold under the central assumptions. High complete two-dose-series coverage remains theoretically capable of reaching the threshold but is operationally demanding. Sustained routine two-dose delivery, high-reach SIAs, and restoration of immunisation-system capacity are likely to be required. The surveillance comparison is retrospective and supports geographic concordance rather than external model validation.

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