Associations of vaccination, recent diarrheal illness, and household environmental conditions with childhood multimorbidity in East Africa

Childhood undernutrition and anemia remain major public health challenges in sub-Saharan Africa. This study investigated the pathways through which vaccination status, environmental conditions, and infectious morbidity jointly influence childhood multimorbidity among seven East African countries. We analyzed nationally representative Demographic and Health Survey data from Burundi, Ethiopia, Kenya, Madagascar, Rwanda, Tanzania, and Uganda, including 30,910 children aged 0 to 59 months. Childhood multimorbidity was defined as the co-occurrence of stunting, underweight, and anemia. A composite environmental index was constructed using indicators of improved water source, sanitation, and clean household cooking fuel. Survey weighted logistic regression models were used to examine associations with recent diarrheal illness, survey weighted Poisson regression models were used to evaluate childhood multimorbidity and mediation analysis was conducted to examine hypothesized associational pathways linking vaccination status, recent diarrheal illness, and childhood multimorbidity. Overall, 33% of children were stunted, 17.6% were underweight, and 45% were anemic. Full vaccination was strongly associated with lower infection incidence (OR = 0.19; 95% CI: 0.17–0.22) and reduced multimorbidity burden (IRR = 0.21; 95% CI: 0.18–0.23) compared with non-fully vaccinated children. Improvements in the environmental index were associated with lower infection incidence (OR = 0.95; 95% CI: 0.93–0.97) and lower multimorbidity burden (IRR = 0.97; 95% CI: 0.95–0.98). Recent diarrheal illness was significantly associated with higher multimorbidity burden (IRR = 1.05; 95% CI: 1.03–1.06). Mediation analysis suggested that recent diarrheal illness statistically explained a small proportion of the observed association between vaccination status and childhood multimorbidity. Childhood multimorbidity in East Africa was associated with vaccination status, household environmental conditions, recent diarrheal illness, and socioeconomic disadvantage. The observed associations are consistent with interconnected pathways linking these factors, although causal relationships cannot be established using cross-sectional data. Full vaccination and improved household environmental conditions were strongly protective against both infection and multimorbidity. Integrated interventions combining immunization strengthening, environmental improvement, infection prevention, and nutritional support may reduce the burden of childhood multimorbidity across East Africa.