INTRODUCTION:
Frontline health workers, including accredited social health activists (ASHA), auxiliary nurse midwives (ANM), and anganwadi workers (AWW), play a critical role in routine immunization delivery in dense urban settlements. Capacity gaps in counselling, due list management, and community engagement may reduce coverage and hinder timely vaccination. This study assesses the impact of structured capacity-building interventions implemented across six urban primary health centres (UPHCs) between October 2024 and October 2025.

METHODS:
A series of 48 ASHA meetings, 48 capacity-building batches, 48 AWW meetings, and 51 review meetings with ANM and medical officers were conducted. Training modules included antenatal care, breastfeeding, complementary feeding, nutrition, and communication skills for immunization promotion. Pre and post assessments measured changes in knowledge. Operational indicators including home visits, counselling interactions, and due list maintenance, were extracted from routine program records.

RESULTS:
Knowledge improved significantly across all domains: antenatal care (65% to 98%), breastfeeding and complementary feeding (16 % to 61 %), nutrition and diet diversity (19% to 96%), and child nutrition (37 % to 72 %). Improved competencies contributed to 1093 home visits, strengthened refusal counselling and due list tracking. These efforts supported the vaccination of 595 previously missed children and facilitated full immunization for 150 children during the study period.

CONCLUSIONS:
Structured and continuous capacity-building strengthened frontline worker competencies and improved routine immunization performance in underserved urban communities. Integrating competency-based training with microplanning and supportive supervision can improve caregiver trust, service quality, and immunization coverage.