The initiative, known as the Big Catch-Up and led by the World Health Organization, UNICEF and Gavi, the Vaccine Alliance, concluded in March after a three-year effort to restore immunization coverage disrupted by the pandemic.

By the end of December 2025, the campaign had reached an estimated 18.3 million children aged under five across 36 countries in Africa and Asia, delivering more than 100 million vaccine doses, according to a joint statement. Of those, around 12.3 million children had never received any prior vaccination, while 15 million had not previously been immunized against measles.

Health systems worldwide faced severe disruption during the COVID-19 crisis, leading to missed routine immunizations and a resurgence of preventable diseases including measles and polio. The agencies said the campaign also strengthened national immunization systems by improving their ability to identify children who had previously been missed.

Tedros Adhanom Ghebreyesus said the initiative had helped reverse one of the pandemic’s major health setbacks by reaching children who had been excluded due to service disruptions.However, officials warned that significant obstacles persist.

The agencies highlighted declining foreign aid and widening gaps in routine immunization, noting that measles outbreaks have increased globally, with approximately 11 million cases reported in 2024.Kate O’Brien said growing politicization of vaccines and health issues posed a serious concern, even as trust in frontline health workers remained relatively strong.

Sania Nishtar pointed to the role of social media in amplifying misinformation, saying digital platforms often incentivize the spread of misleading or false content about vaccines.

Ephrem Lemango added that algorithm-driven amplification of anti-vaccine narratives, combined with reductions in global health funding, could undermine progress and risk reversing gains made through the campaign.