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

•Factors enabling migration, rather than migration itself, influence child vaccination.•The migration stream did not differentially influence child vaccination.•Multiply imputed estimates of vaccination allowed inclusion of children without cards.•Up-to-date vaccination was lower when children without cards were included. 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. 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. 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. 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.