Case studies of Big Catch-Up immunization in low- and middle-income countries

© WHO / Ochemba Chimaobi
Aishatu is a vaccinator in her Local Government Area, in Kano State, determined to ensure no child is missed is fight against vaccine preventable diseases.

Overview

Persistent challenges, compounded by setbacks during the COVID-19 pandemic, have left millions of children under-immunized. This project looks at Big Catch-Up activities in five countries to understand what worked, what didn’t and how future efforts can be strengthened.

About the project

The Big Catch-Up (BCU): An Essential Immunization Recovery Plan is a global initiative to support countries to plan and implement intensified efforts to bolster immunization programmes in the context of reverses in immunization coverage catalysed by the disruptions to health services during the COVID-19 pandemic.

The Alliance is supporting case studies in Cameroon, Nigeria, Pakistan, the United Republic of Tanzania and Yemen. Each study examines how Big Catch-Up was planned, implemented and institutionalized, with the aim of informing better strategies to close gaps and reach children left behind.

Why it matters

The Big Catch-Up was launched to tackle long-standing inequalities in immunization – inequalities that deepened during the COVID-19 pandemic. By early 2023, many immunization activities had not resumed to earlier levels, leaving millions of children under-immunized and at higher risk of outbreaks from vaccine-preventable diseases.

Although countries are working to restore services, more evidence is needed on how children can be caught up. Understanding these gaps is critical to building stronger, more resilient health systems.

Our approach

The Alliance is working with WHO’s Immunization, Vaccines and Biologicals Department to generate evidence and draw lessons from country experiences with the Big Catch-Up. Independent research teams in each country are examining:

How Big Catch-Up activities were planned and implemented, and the challenges faced;
How countries are making catch-up efforts part of routine systems for long-term resilience; and
Why some children continue to miss vaccinations despite efforts to close the gap.

People, places and partnerships

Five national research partners are leading the case studies:

Cameroon: EVIDHAF (Evidence for Sustainable Human Development Systems in Africa)
Nigeria: Health Policy Research Group, University of Nigeria–Enugu, and Brooks Insights
Pakistan: CERP and Rayn
United Republic of Tanzania: The Catholic University of Health and Allied Health Sciences
Yemen: Building Foundation for Development

Learning and evidence

Aiming for impact

Achieving impact is a guiding principle that shapes our work and 2024–2028 strategy. Success can take many forms, all of which can contribute to stronger, more resilient health systems. This project is contributing to real-world improvements in health systems in part through:

Shifting the frame: Challenging assumptions about what it takes to reach under-immunized children, exploring how countries are embedding catch-up within broader health systems to strengthen delivery for those hardest to reach.
Changing practices: Analysing implementation efforts to identify what works, highlight obstacles and note areas fo improvement.
Building connections: Fostering learning between contexts on what works to strengthen catch-up activities long-term.
Informing policies and processes: Providing guidance on how to institutionalize catch-up and improve immunization coverage, especially for vulnerable populations.