Recent studies in Nairobi slums have highlighted significant gaps in immunization coverage among children under five years of age. The analysis is based on a longitudinal study conducted over five years, tracking changes in immunization uptake before and after network expansion across Nairobi slums. Community health workers played a critical role in increasing routine childhood vaccinations by nearly 30% within the first year of expanded networks, particularly among underprivileged communities. The findings suggest that targeted community engagement can significantly boost immunization rates and improve child health outcomes in Nairobi slums. Implementing sustainable community health worker programmes should be prioritised to maintain high immunization coverage and address vaccine hesitancy effectively.