Risk-factors Associated with Non-Vaccination in Gambian Children: A Population-Based Cohort Study

ObjectiveWe determined the risk-factors associated with children who remain unvaccinated in rural Gambia. MethodsWe conducted prospective demographic surveillance and recorded immunisations in real-time in the Basse Health and Demographic Surveillance System. Analysis included residents born between January 1, 2012 and December 31, 2016. Demographic data included age, sex, household members and relationships, migrations, births, deaths, ethnicity, residential location, and birth type. Children were defined as unvaccinated at 10-, 15-, and 24-months of age, if they missed all primary series doses (pentavalent, oral polio and pneumococcal conjugate vaccines), secondary series (1st dose measles and yellow-fever vaccines) or both vaccination series, respectively. Multivariate three-level mixed effects logistic regressions measured the strength of association between risk-factors and being unvaccinated at age 10-, 15-, and 24-months. Findings38,090 infants were born during the study period, while 30,832 survived as residents and 1,567 were unvaccinated at age 10 months. Being unvaccinated at 10-months of age was associated with children not residing with their father (adjusted odds ratio [aOR] 1.38, 95% CI 1.22-1.58) or mother (aOR 2.94, 95% CI 1.33-6.46) or both parents (aOR 2.26, 1.60-3.19), whose parents were not the head of household (aOR 1.29 (1.09-1.52), experiencing external in-migration (aOR 2.78, 95% CI 1.52-5.08) and not of Mandinka ethnicity (aOR varied between 1.57 to 1.85 for three other ethnicities). ConclusionUnimmunised children in rural Gambia are more likely to not live with their parents and have migrated into the area. These results may inform strategies to increase vaccine coverage.