Prevalence of zero-dose vaccination and its associated factors in urban areas of Somali region, Ethiopia: a mixed-methods approach.

Introduction: Despite global progress in immunisation, vaccine coverage remains uneven in many low- and middle-income countries. Urbanisation has widened disparities, particularly among children in informal settlements. Ethiopia has a high zero-dose burden, with the Somali region identified as a hotspot. However, urban areas in this region remain understudied. This study assesses the prevalence of zero-dose children and associated factors in urban areas of the Somali region to inform targeted interventions. Methods: Using a mixed-methods approach, data were collected from 842 households in three urban towns through community surveys and six key informant interviews. The primary outcome was the proportion of zero-dose children, defined as those who had not received the first dose of the DTP-containing vaccine (Penta-1) during their first year of life, based on vaccination card records or caregiver recall. This included children who had never received any vaccine or had received some vaccines but not Penta-1. Quantitative data were analysed using logistic regression, while qualitative findings were examined thematically using the GAVI IRMMA framework. Strict quality control measures ensured the reliability of results. Results: Of 842 targeted households, 827 participated (98.2% response). Findings reveal that 30% of children surveyed were identified as zero-dose for vaccination. Children were significantly more likely to be zero-dose if their mothers had no antenatal care (adjusted OR, AOR ~5.0), required permission for vaccination (AOR ~3.4), delivered at home (AOR ~3.1), or did not receive the second dose of tetanus toxoid (AOR ~2.7). In contrast, higher perceived household wealth and at least one postnatal care visit reduced the likelihood of zero-dose by about 45% and 55%, respectively. Zero-dose children were concentrated in urban peripheries and informal settlements with limited healthcare access, poor identification strategies and reliance on facility-based vaccination services. Conclusions: The study highlights a higher prevalence of zero-dose children in urban areas, underscoring the urgent need for improved identification and mapping in underserved communities. Strengthening advocacy, diversifying immunisation approaches and addressing systemic barriers are essential to improving vaccine access and reducing the zero-dose burden.