Global ''Big Catch-Up'' Initiative Reaches 18.3 Million Children with Over 100 Million Vaccine Doses, but Routine Immunization Gaps Persist
Introduction
A multi-year global vaccination campaign called the Big Catch-Up (BCU) has delivered more than 100 million vaccine doses to an estimated 18.3 million children aged one to five across 36 countries, mainly in Africa and Asia. The initiative started in April 2023 and ended in March 2026. Its goal was to stop the decline in childhood immunization caused by the COVID-19 pandemic. According to Gavi, the Vaccine Alliance, the World Health Organization (WHO), and UNICEF, the program is on track to reach its target of at least 21 million children who were not vaccinated or only partly vaccinated, although final data are still being collected.
Main Body
The BCU was a coordinated response to pandemic-related disruptions that put pressure on health systems and led to a return of vaccine-preventable diseases such as measles and polio. Of the children reached between 2023 and 2025, about 12.3 million were classified as ''zero-dose'' – meaning they had never received any vaccine – and 15 million had not previously received a measles vaccine. In addition, 23 million doses of inactivated polio vaccine were given to un- or under-vaccinated children. The 36 participating countries are home to 60% of all zero-dose children worldwide, according to the agencies. The initiative focused on children aged one to five, a group that had become too old for the usual infant vaccination schedules. For the first time, the BCU used routine immunization systems to find, check, and vaccinate these older children. Participating countries updated age rules, trained health workers, and worked with communities to support catch-up efforts. Twelve countries – including Burkina Faso, Ethiopia, Kenya, Niger, Pakistan, and Zambia – reported reaching more than 60% of zero-dose children under five who had missed the first dose of the diphtheria-tetanus-pertussis (DTP1) vaccine. Ethiopia alone reached over 2.5 million previously zero-dose children with DTP1 and gave nearly 5 million doses of IPV and over 4 million doses of measles vaccine. Despite these achievements, the agencies emphasized that catch-up vaccination is an additional measure, not a replacement for strong routine immunization. In 2024, an estimated 14.3 million infants worldwide did not receive a single routine vaccine. The results are clear: measles outbreaks have increased in every region, with about 11 million cases recorded in 2024, and the number of countries experiencing large outbreaks has nearly tripled since 2021. The agencies said this rise is due to ongoing gaps in routine measles vaccination, made worse by falling vaccine confidence in some areas that previously had high coverage. Officials from the three organizations also pointed to other challenges. WHO vaccines director Kate O’Brien noted a growing political influence on vaccines and health. Gavi CEO Sania Nishtar stated that social media algorithms encourage the spread of false information, which she said requires strategic actions to fight it. UNICEF’s global chief of immunization, Ephrem Lemango, observed that algorithms often spread angry content more than accurate information and that there is a market for anti-vaccine material. Lemango also warned that recent large funding cuts to global health – including the U.S. decision to reduce financial support for Gavi, announced by Health Secretary Robert F. Kennedy Jr. – have seriously affected immunization services and could reverse progress that was difficult to achieve.
Conclusion
The Big Catch-Up has shown that targeted investment and political will can reduce immunization gaps among older children. However, the fact that millions of infants still miss routine vaccines each year, combined with rising measles outbreaks, funding reductions, and the spread of vaccine misinformation, highlights the need for continued domestic investment and reliable donor commitments. The agencies argue that strengthening routine immunization systems remains the most effective and sustainable way to protect children and prevent future outbreaks.