The influence of maternal migration on child vaccination in Kenya: An inverse probability of treatment-weighted analysis

OBJECTIVES: Kenya has substantially improved child mortality between 1990 and 2019, with under-5 mortality decreasing from 104 to 43 deaths per 1000 live births. However, only two-thirds of Kenyan children receive all recommended vaccines by 1 year, making it essential to identify undervaccinated subpopulations. Internal migrants are a potentially vulnerable group at risk of decreased access to healthcare. This analysis explored how maternal migration within Kenya influences childhood vaccination. METHODS: Data were from the 2014 Kenya Demographic and Health Survey, a nationally representative cross-sectional survey. Logistic regressions assessed relationships between maternal migration and full and up-to-date child vaccination using inverse probability of treatment weighting. Two exposure variables were examined: migration status and stream (e.g. rural-urban). Multiple imputation was used to impute up-to-date status for children without vaccination cards to reduce selection bias. RESULTS: After accounting for selection and confounding biases, all relationships between migration status and migration stream and full and up-to-date vaccination became statistically insignificant. CONCLUSIONS: Null findings indicate that, in Kenya, characteristics enabling migration, rather than the process of migration itself, drive differential vaccination behavior between migrants and non-migrants. This finding is an important deviation from previous literature, which did not rigorously address important biases.