Post-COVID Vaccination Catch-Up Campaign Reaches 18.3 Million Children, But Challenges Loom

A massive global effort to vaccinate children who missed immunizations during the COVID-19 pandemic has successfully reached 18.3 million children, including 12.3 million who had never received any vaccines, global health leaders reported Thursday.

The campaign, known as the “Big Catch-Up,” delivered over 100 million vaccines between 2023 and 2025, with 15 million children receiving their first measles vaccine. The initiative specifically targeted 36 countries that accounted for 60% of the world’s “zero-dose” children – those who had never received any immunizations.

“By 2021, coverage of the three-in-one diphtheria, tetanus and pertussis vaccine had fallen to 78% in lower-income countries, erasing years of hard-won gains,” explained Dr. Sania Nishtar, CEO of Gavi, the Vaccine Alliance, during a media briefing ahead of World Vaccination Week.

The campaign actively sought children under five who had missed vaccines, with particularly strong results in twelve countries that reached more than 60% of their zero-dose children: Burkina Faso, Democratic People’s Republic of Korea, Ethiopia, Kenya, Madagascar, Mauritania, Niger, Pakistan, Somalia, Togo, Tanzania, and Zambia.

“In total, catch-up reached the equivalent of five times the number of children under five in the European Union,” Nishtar noted.

Beyond simply delivering vaccines, the initiative strengthened countries’ immunization systems, according to Dr. Kate O’Brien, WHO’s immunization director. This included extending monitoring of children’s immunization status from age two to age five and enhancing primary health care systems to better track newborns.

Funding Crisis Threatens Progress

Despite the campaign’s success, global health officials warned that shrinking international aid threatens to undermine these gains. Dr. Ephrem Lemango, UNICEF’s global chief of immunization, highlighted that “the continued decline of official development assistance and recent sharp funding cuts to global health have seriously affected the delivery of immunization services.”

The reduction in international aid has impacted crucial “last-mile” outreach efforts that depend on health workers and supply chains supported by these funds. Additionally, some governments are struggling to provide their share of co-financing to procure vaccines through Gavi.

Countries that traditionally received donor funds for vaccines against polio, tuberculosis, and other diseases have seen this support “considerably disrupted,” Lemango explained. The funding cuts have also limited the capacity of WHO, UNICEF, and Gavi to provide technical assistance to governments.

O’Brien added that diminished aid has weakened the ability of countries and international agencies to respond rapidly to disease outbreaks. However, Nishtar pointed to a “silver lining” in Africa’s emerging “health sovereignty movement,” where heads of state are emphasizing the need to deliver basic services through domestic revenue.

Misinformation Threatens Vaccine Confidence

Beyond funding challenges, health officials identified vaccine misinformation as a growing threat to immunization efforts worldwide.

“Trust has become a prominent predictor of vaccine uptake across countries and populations,” Lemango warned. “Even brief exposure to vaccine misinformation likely reduces the willingness to vaccinate.” He noted that much anti-vaccine content has “its own political economy behind it, where there is financial and political backing.”

While skepticism about vaccines has always existed, social media has dramatically amplified misinformation, according to Nishtar. O’Brien expressed particular concern about the increasing politicization of vaccines and health issues.

“Politicization of vaccines should not happen,” O’Brien stressed. “The world of vaccines should be based on evidence and facts and should be supportive of families and children’s parents or caregivers to provide what is a life-saving intervention for them.”

As the global health community celebrates the success of the Big Catch-Up campaign, maintaining momentum will require addressing these dual challenges of diminished funding and growing misinformation, while continuing to focus on reaching vulnerable populations in fragile and conflict-affected regions.