Big Catch-Up drive delivers 100 million vaccine doses to 18.3 million children

What is the background?

Childhood vaccination rates dropped sharply worldwide during the COVID-19 pandemic, leaving millions of children without protection against preventable diseases. The World Health Organization (WHO), UNICEF, and Gavi, the Vaccine Alliance launched the Big Catch-Up during World Immunization Week 2023 to find and vaccinate children who had missed routine shots before they aged out of standard immunization schedules.

What happened?

By the time the programme concluded on 31 March 2026, it had delivered more than 100 million vaccine doses to an estimated 18.3 million children aged 1 to 5 across 36 countries in Africa and Asia. Around 12.3 million of those children were “zero-dose” children who had never received any vaccine, and 15 million had never received a measles dose. The initiative also provided 23 million doses of inactivated polio vaccine to under-vaccinated children. WHO, UNICEF, and Gavi announced the final figures in a joint news release on 24 April 2026, at the start of World Immunization Week, reporting the effort is on track to meet its target of reaching 21 million under-immunized children.

How did it happen?

Rather than focusing only on infants, the Big Catch-Up used routine immunization systems to reach older children between ages 1 and 5 who had already missed scheduled vaccines, a first-time approach at this scale according to the agencies. Participating countries updated policies on vaccination age eligibility, trained health workers to identify and vaccinate missed children during routine visits, and engaged community and civil society groups to locate children who had fallen through the cracks.

Twelve of the 36 countries — Burkina Faso, the Democratic People’s Republic of Korea, Ethiopia, Kenya, Madagascar, Mauritania, Niger, Pakistan, Somalia, Togo, Tanzania, and Zambia — reached more than 60 percent of their zero-dose children under five. Ethiopia delivered first doses of the DTP vaccine to 2.5 million previously zero-dose children, alongside nearly 5 million polio doses and more than 4 million measles doses.

Why does it matter?

The 36 participating countries account for 60 percent of all zero-dose children worldwide, so the initiative targeted the populations facing the steepest immunization gaps, many in fragile or conflict-affected settings. “The Big Catch-Up shows what is possible when governments, partners and communities work together to protect the most vulnerable in society,” said Dr Sania Nishtar, CEO of Gavi, the Vaccine Alliance. WHO Director-General Dr Tedros Adhanom Ghebreyesus said the effort left national immunization programmes “better equipped to find and vaccinate children missed by routine services.” Agencies caution that catch-up campaigns cannot replace routine immunization, especially as measles cases reached around 11 million in 2024 and outbreaks have nearly tripled since 2021.

What were the key results?

• Over 100 million vaccine doses delivered to 18.3 million children across 36 countries
• 12.3 million “zero-dose” children received a vaccine for the first time
• 15 million children reached with their first-ever measles vaccine dose
• 23 million doses of inactivated polio vaccine administered to support polio eradication
• Ethiopia delivered DTP1 to 2.5 million zero-dose children, plus nearly 5 million polio doses
• Nigeria reached 2 million zero-dose children with DTP1 and gave 3.4 million polio doses

What happens next?

WHO, UNICEF, and Gavi are marking World Immunization Week 2026 with a new joint campaign, “For every generation, vaccines work,” urging countries to sustain coverage gains reached during the catch-up drive.

Agencies warn that an estimated 14.3 million infants still missed routine vaccination in 2024, and say closing that gap will require long-term investment in routine immunization systems rather than repeated catch-up campaigns.

Gavi’s 2026-2030 strategy, known as Gavi 6.0, keeps reaching zero-dose children in fragile and conflict-affected settings as a central priority.

Countries that took part in the Big Catch-Up are expected to keep using the eligibility policy changes and health worker training built during the programme to find newly missed children going forward.