Childhood immunization rates in Nairobi slums have been suboptimal despite the availability of free healthcare services and vaccines. A meta-analysis was conducted using data from multiple studies published between and that assessed CHW training initiatives aimed at improving immunization coverage in these areas. Studies were selected based on their methodological quality and relevance to the research question. CHW training significantly increased childhood immunization rates by an average of 15% (95% CI: 7-23%) compared to control groups without CHW interventions. Community health worker training appears effective in enhancing childhood immunization rates in Nairobi slums, with notable improvements observed in the most vulnerable populations. Implementing and sustaining CHW training programmes should be prioritised as a key strategy for improving vaccination coverage in underserved urban areas. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.