Barriers and facilitators of childhood immunization: sociodemographic and knowledge-related determinants among parents in rural and urban Khyber Pakhtunkhwa, Pakistan.

Immunization is critical for reducing vaccine-preventable disease morbidity and mortality, yet coverage disparities persist in low-resource settings. This mixed-methods study describes characteristics of childhood immunization defaulters and explores barriers to vaccine adherence in Khyber Pakhtunkhwa, Pakistan. We recruited 380 caregivers from three tehsils in District Kohat of Khyber Pakhtunkhwa from February to July 2023, whose children under 2 years had not completed the Expanded Program on Immunization (EPI)-recommended schedule. Quantitative data from validated questionnaires and immunization cards underwent descriptive and regression analyses; qualitative interviews explored non-adherence reasons. Most respondents were fathers (96.05%); 41.84% resided in rural areas. Initial coverage was high for BCG (97.89%) and OPV0 (100%) but declined for Penta3 (26.05%) and Measles2 (4.21%). Most children (73.95%) were under 4 months. Rural defaulters were more prevalent than urban (41.84% vs. 34.47%, p < 0.001), and 89.47% had mothers with ≤high school education. While 95.26% had heard of vaccines, only 49.47% knew the EPI starting age. Defaulters with higher knowledge progressed further through the schedule (AOR: 4.55, p = 0.05). Qualitative themes included poor healthcare access, cultural norms, religious misconceptions, and migration disruptions. Interventions addressing maternal education, rural access, and knowledge gaps are essential to reduce immunization default.