Global ‘big catch-up’ initiative rescues 18.3 Million children from post-pandemic immunity gap

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 Key points

• Massive Scale: The “Big Catch-Up” (BCU) delivered over 100 million vaccine doses to children aged 1–5 between 2023 and 2025, successfully navigating the “immunity debt” left by COVID-19.

• Targeting the “Zero-Dose” Crisis: Out of 18.3 million children reached, 12.3 million were “zero-dose” individuals who had never received a single vaccination prior to this intervention.

• Systemic Overhaul: Beyond temporary clinics, the program successfully integrated older children (aged 1–5) into routine immunization systems—a first for global health policy on this scale.

Main story

A sweeping global health offensive launched in the wake of the COVID-19 pandemic has successfully reached 18.3 million children across 36 countries, effectively “restarting” the heart of routine pediatric care.

Findings released by Gavi, the World Health Organization (WHO), and UNICEF to mark World Immunization Week 2026 reveal that the Big Catch-Up (BCU) initiative has delivered 100 million doses of life-saving vaccines, clawing back ground lost during years of global lockdown and healthcare disruption.

The campaign specifically targeted the “lost cohort” children who aged out of traditional infant immunization windows while clinics were shuttered or overwhelmed.

The effort proved particularly effective in Africa and Asia, with countries like Ethiopia and Nigeria together vaccinating over 4.5 million previously “zero-dose” children. As the program concluded in March 2026, data suggests the initiative is on a firm trajectory to hit its ultimate target of 21 million under-immunized children.

The issues

Despite these historic gains, the global health landscape remains precarious. The report highlights a widening equity gap, as the 36 participating nations account for roughly 60% of the world’s unvaccinated children, many of whom reside in fragile, conflict-ridden zones.

Furthermore, the “Big Catch-Up” was necessitated by a grim reality: an estimated 11 million measles cases were reported in 2024 alone, a sharp rise attributed to declining coverage and rising vaccine hesitancy. While the BCU administered 23 million doses of inactivated polio vaccine (IPV) and millions of measles shots, the sheer volume of infants still missing their first routine doses—14.3 million in 2024—remains a significant threat to global health security.

What’s being said

Dr. Tedros Adhanom Ghebreyesus, WHO Director-General: > “By protecting children who missed out on vaccinations because of disruptions to health services, the Big Catch-Up has helped to undo one of the pandemic’s major negative consequences.”

Catherine Russell, UNICEF Executive Director said “We’ve reached millions… but many more remain out of reach. Progress must be sustained through long-term investment in health systems.”

Dr. Sania Nishtar, Gavi CEO  stated that “This effort shows what is possible when governments, partners, and communities work together to protect the most vulnerable.”

What’s next

As the global community enters the midpoint of the Immunization Agenda 2030, the focus shifts from “emergency catch-up” to “permanent fortification.” Health agencies are urging governments to move beyond resource-intensive one-off campaigns. The next phase involves institutionalizing the screening and monitoring systems developed during the BCU to ensure that the expansion of age eligibility for vaccines becomes a permanent fixture of national health policies.

Bottom line

The Big Catch-Up has successfully bridged the most dangerous gap in modern immunization history, but it is a temporary fix for a structural problem. While 18.3 million children are safer today, the ultimate survival of global pediatric health depends on the transition from a “catch-up” mentality to a robust, resilient, and routine system that leaves no child behind.