Maternal Mortality, Adolescent Fertility, and Immunization as Drivers of Under‐Five Mortality: A 187‐Country Panel, 1992–2023

AIM: To quantify the long-term associations between adolescent fertility (AFR), maternal mortality (MMR), immunization coverage, and under-five mortality (U5MR) across countries and regions. METHODS: A strongly balanced panel of 187 countries (1992-2023) was constructed using World Bank and WHO data. The primary outcome was U5MR (deaths before age five per 1000 live births). Exposures included AFR (births per 1000 women aged 15-19), MMR (per 100 000 live births), full immunization (%), and measles (MCV1) coverage (%). Two-way panel regression models with country and year effects were estimated under fixed and random effects, guided by the Hausman test. Inference used Driscoll-Kraay or cluster-robust standard errors. Robustness checks incorporated lagged covariates, correlated random effects, common-correlated-effects models, and a vaccination composite. RESULTS: Globally, higher AFR and MMR were consistently linked to increased U5MR, while full immunization was protective. Each 10-per-1000 increase in AFR corresponded to about 4.6 additional under-five deaths per 1000, each 10-percentage-point increase in full immunization to 4.9 fewer, and each 100-per-100 000 increase in MMR to 8.8 more. Measles coverage showed additional protective effects in Asia and the Americas. AFR was the strongest predictor in Africa, while MMR was a near-universal predictor across regions. CONCLUSION: U5MR remains strongly tied to adolescent fertility, maternal survival, and immunization. Region-specific, equity-focused interventions-expanding adolescent reproductive health services, high-quality maternal care, and comprehensive immunization (including at least 95% two-dose measles coverage)-are essential to accelerate progress towards Sustainable Development Goal 3.2.