Institutionalizing learning by mainstreaming embedded implementation research in country immunization programmes (MAINSTREAM) (2023–2025) set out to institutionalize learning in immunization programmes by embedding implementation research (IR) where decisions are made.

Working in Cameroon, Ghana, Madagascar, Malawi, Mozambique and Pakistan, mentor institutes convened local immunization stakeholders to define priority learning questions, support 25 rapid IR projects, and translate results into operational adjustments that help find and serve zero-dose (ZD) and underimmunized children. The work confirms that short, embedded cycles can produce usable solutions at programme speed—while building the capabilities and relationships required for sustained improvement.

Key messages:

1. Embedded IR delivers programme ready solutions. Across six countries, 25 locally led IR projects generated feasible actions. Concrete gains include improved appointment adherence with text message reminders, high conversion of health worker referrals to vaccinations, flexible clinic hours that families actually use, and digital monitoring that targets ZD hotspots for action.
2. The mentor institute model builds durable country capacity. Country based mentor institutes strengthened IR skills of local teams, deepened ties with immunization programmes, and catalyzed networks
   that can continually diagnose problems and adapt solutions to strengthen immunization. 
3. Programmes want more: demand from immunization programmes outstrips current supply of IR. Immunization decision-makers showed strong appetite to commission and use IR. Priority-setting exercises surfaced more actionable questions than a single round could cover; the 25 projects only scratched the surface of priority learning agendas identified through national workshops.
4. Short cycles work—but institutionalization needs time. Ethics timelines, operational crises, and the depth of systems issues mean sustained funding is essential to convert tested solutions into institutionalized policy and routine practice. 
5. Continued investment will accelerate equity gains. MAINSTREAM surfaced scalable, context specific strategies for finding and serving ZD children. Dedicated funds for locally led IR and knowledge translation will accelerate uptake and protect results against turnover and shocks.