To better understand low immunization uptake, a pilot study tested a Decentralized Immunization Monitoring (DIM) approach in Kumbotso, Kano State, Nigeria. Using lot quality assurance sampling  and the behavioral and social drivers of vaccination framework, researchers identified wards with low vaccination rates and explored the reasons why. The findings were used to improve routine immunization programs and reduce the number of unvaccinated children and children yet to receive their first dose of diphtheria–pertussis–tetanus vaccine, referred to as zero-dose (ZD) children. Key barriers included low caregiver education, rural residence, and negative vaccine perceptions. The study highlights the value of decentralized monitoring and community engagement to strengthen routine immunization and reach ZD children.