The WHO Regional Office for South-East Asia (WHO-SEARO) convened the subnational implementation review workshop of the Big Catch-Up (BCU) immunization initiative in New Delhi on 10–12 December 2025, bringing together national and subnational immunization managers, technical experts and WHO staff members from Nepal, Myanmar, India and Timor-Leste, alongside WHO personnel from the Regional Office and headquarters. Key partners – including the United Nations Children’s Fund (UNICEF), Gavi, the Vaccine Alliance (Gavi), Program for Appropriate Technology in Health (PATH), John Snow India (JSI) and Immunization Technical Support Unit (ITSU) – joined the workshop to jointly review BCU progress and shape strategies for institutionalizing catch-up vaccination.

The workshop highlighted significant recovery since the launch of the BCU initiative in 2023 to address immunity gaps widened by COVID-19. Countries reported meaningful reductions in zero-dose children, improved antigen coverage and increasing integration of catch-up into routine systems. Despite progress, participants acknowledged ongoing challenges, including coverage inequities, data quality issues, resource constraints and workforce limitations. Countries identified key priorities: developing country-owned workplans, strengthening real-time data systems, sustaining partner engagement, and prioritizing approaches for vulnerable and underserved populations. The BCU workshop served as a critical regional platform to consolidate evidence, share practical solutions and reinforce collective commitment to institutionalizing catch-up vaccination across the Region.