Determinants of Immunisation Drop-Out Among Children Aged 6–59 Months in the Urban-Rural Health Zone of Mbandaka, Democratic Republic of the Congo

In developing countries, under-immunisation and high vaccine drop-out rates remain a major concern across all levels of the healthcare system. This study aimed to identify the underlying factors that contribute to the abandonment of vaccination by parents or guardians of children eligible for immunisation. Using a quantitative case-control design, the study compared caregivers of children aged 6 to 59 months who dropped out of the vaccination program (cases) with those whose children followed the vaccination schedule consistently (controls), within a population of 6,152 children in the Mbandaka health zone. Data were collected through structured questionnaires and processed using Excel 2010 and SPSS 2025. The findings revealed that being in the case group was strongly associated with vaccine drop-out (HR=2.53), as well as belonging to a medium-income household (HR=1.84), being in a polyandrous union (HR=2.92), having illiterate parents (HR=6.04), and residing in the central antenna zone (HR=1.93). These results highlight the urgent need for the health zone to reinforce awareness campaigns targeting parents and decision-makers and to enhance vaccine distribution in remote areas to reduce social inequalities in immunisation coverage.