Association Between Routine Childhood Immunization Coverage and Under-Five Mortality in Sub-Saharan Africa: An Ecological Panel Study, 2000–2024

Abstract Background Under-five mortality remains a major public health challenge in sub-Saharan Africa. Across sub-Saharan Africa, the mean under-five mortality rate declined by 57%, from 131.0 to 56.6 deaths per 1,000 live births between 2000 and 2024, indicating substantial progress but a persistently high regional burden. Routine childhood immunization is among the most effective child survival interventions, but the long-term ecological relationship between vaccine coverage and under-five mortality across the region remains important to quantify. Methods We conducted an ecological panel study using annual country-level data from sub-Saharan African countries between 2000 and 2024. Under-five mortality rate, expressed as deaths per 1,000 live births, was the outcome. Immunization coverage indicators included DTP3, MCV1 and Pol3 coverage. Covariates included GDP per capita, current health expenditure per capita, total fertility rate, access to basic drinking water and access to basic sanitation. Multivariable linear regression models were fitted separately for each antigen. Country and year fixed-effects models were used to account for unobserved country-level heterogeneity and secular trends. Sensitivity analyses included restricted analyses excluding relatively wealthier sub-Saharan African countries and lagged exposure models. The assembled panel covered 2000–2024; the complete-case primary models used observations through 2023 because current health expenditure per capita was unavailable for all included countries in 2024. Results The assembled panel included 49 sub-Saharan African countries and 1,225 country-year observations; 1,108 complete observations from 48 countries were included in the primary models. In the adjusted model, each 1-percentage-point increase in DTP3 coverage was associated with 0.97 fewer under-five deaths per 1,000 live births (95% confidence interval [CI], − 1.30 to − 0.64), equivalent to approximately 9.7 fewer deaths per 1,000 live births for a 10-percentage-point increase in coverage. In the country-and-year fixed-effects model, higher DTP3 coverage within countries over time was associated with lower under-five mortality: each 1-percentage-point increase was associated with 0.28 fewer deaths per 1,000 live births (95% CI, − 0.563 to − 0.002), equivalent to approximately 2.8 fewer deaths per 1,000 live births for a 10-percentage-point increase in DTP3 coverage. Conclusions Higher routine childhood immunization coverage, particularly DTP3 coverage, was consistently associated with lower under-five mortality at the country-year level. Strengthening routine immunization should remain part of integrated child-survival strategies alongside improvements in health systems and social determinants of health.