OpenCHANJO is a digital health tool aimed at improving immunization efforts in Kenya by addressing the issue of zero-dose immunization through better data tracking and defaulter tracing. It supports both routine and non-routine vaccines while adhering to WHO SMART guidelines to ensure standards-based care, scalability, and interoperability. The system features offline capabilities, clinical decision support, and timely immunization alerts, enhancing data management and offering actionable insights through an interactive dashboard. Its focus includes implementing a comprehensive digital immunization registry, ensuring international standards compliance, and enhancing healthcare providers' capacity to deliver efficient immunization services with guideline-based support and individualized client vaccination schedules, targeting the general population.