Persistent measles immunization gaps in LMICs: Insights from the 2024 revision of the WHO/UNICEF estimates of...

Measles remains a leading vaccine-preventable killer in low- and middle-income countries (LMICs). Using the WHO/UNICEF Estimates of National Immunization Coverage (WUENIC) 2024 revisions, this article assesses measles-containing vaccine first-dose (MCV1) and second-dose (MCV2) coverage trends, inequities, and priority groups for targeted action.

Data from 2019 to 2024 for 137 LMICs were analysed using descriptive statistics; Welch's t-tests and Wilcoxon rank-sum tests to compare fragile versus non-fragile states; Gini coefficients for inequality; k-means clustering (k = 4) on coverage, MCV1-to-MCV2 dropout, change, unvaccinated counts, and fragility; and bounded linear models to project MCV1 to 2030.

In 2024, mean MCV1 coverage was 79.2% (95% CI: 76.8-81.6)-below the 95% threshold-with fragile LMICs at 68.5% versus 87.4% in non-fragile LMICs (difference - 18.1 percentage points; p < 0.001). MCV2 gaps were larger (-26.9 percentage points; p < 0.001). DTP1-based zero-dose prevalence was 20.8%, with 15.6 million children unvaccinated for MCV1 and 22.4 million for MCV2; West and Central Africa accounted for 7.2 million MCV1-unvaccinated (46.2%). Inequality rose (Gini 0.22 → 0.25, 2019-2024). Projections indicate MCV1 of 84.2% by 2030, with fragile LMICs off-track. Clustering identified four profiles: (1) very low coverage, high dropout, high fragility (22 countries); (2) high coverage, low dropout (44); (3) low coverage, severe dropout (31); and (4) low coverage, moderate dropout (40), each implying distinct priorities (conflict-adapted SIAs; sustaining gains; follow-up campaigns; expanding first-dose access).

Persistent and widening measles immunization gaps-especially in fragile settings-threaten IA2030's 90% coverage targets. Pairing the 2024 WUENIC revision with fragility-sensitive clustering and bounded projections provides a practical framework to prioritize equity-focused funding and operational strategies where need is greatest.