By Oluwafunke Ishola
A global vaccination programme inaugurated after COVID-19 has reached 18.3 million children in 36 countries, helping close immunisation gaps and restart routine health services hit by the pandemic.
The programme, known as the Big Catch-Up (BCU), delivered more than 100 million doses of life-saving vaccines to children aged one to five between 2023 and 2025.
Gavi, the Vaccine Alliance, the World Health Organisation (WHO), and UNICEF released the findings to mark the start of World Immunisation Week 2026.
The health agencies said the campaign specifically targeted children who had missed routine vaccinations during the pandemic, when widespread disruptions to health systems led to sharp declines in immunisation coverage worldwide.
Of the total reached, about 12.3 million were “zero-dose” children—those who had never received a single vaccine—while roughly 15 million had not previously been vaccinated against measles, one of the most contagious and deadly childhood diseases.
The initiative also administered 23 million doses of inactivated polio vaccine, a key step toward global eradication of the disease.
Although final figures are still being compiled following the programme’s conclusion in March 2026, the agencies said the effort is on track to meet its target of reaching at least 21 million under-immunised children.
Closing a widening equity gap
Beyond pandemic recovery, the campaign sought to tackle long-standing inequalities in access to vaccines, particularly in fragile and conflict-affected regions.
The 36 participating countries—primarily in Africa and Asia—account for around 60 per cent of the world’s zero-dose children.
The agencies said pandemic exacerbated existing disparities, leaving millions more children without access to routine immunisation services.
In response, the Big Catch-Up expanded its focus beyond infants to include older children aged one to five who had previously been missed by national programmes.
“This is the first time routine immunisation systems have been systematically used at scale to reach older, unvaccinated children.
“BCU catalysed long-lasting systems to identify, screen, vaccinate and monitor coverage rates in these older children – including updates to policies on age eligibility.”
They noted that many of these children had remained vulnerable well beyond infancy.
The initiative also invested in strengthening health systems, training workers to identify and vaccinate missed children, updating eligibility policies, and working with communities to improve uptake.
These measures, they said, are expected to deliver long-term benefits beyond the lifespan of the programme.
Several countries reported significant progress. Ethiopia vaccinated more than 2.5 million previously zero-dose children.
The country also delivered nearly five million doses of IPV and more than four million doses of measles vaccine, among other key vaccines, to un- and under-vaccinated children.
While Nigeria reached around two million such children and administered millions of additional vaccine doses, including for polio and measles.
Twelve participating countries—including Burkina Faso, Kenya, Pakistan, and Tanzania—reported reaching more than 60 per cent of zero-dose children under five who had missed their first routine vaccines.
Warning against complacency
Not withstanding the gains, the agencies cautioned that catch-up campaigns alone cannot address the scale of the problem.
They stressed that strengthening routine immunisation systems remained the most effective and sustainable way to protect children.
“By protecting children who missed out on vaccinations because of disruptions to health services caused by COVID-19, the Big Catch-up has helped to undo one of the pandemic’s major negative consequences,” said Tedros Ghebreyesus, Director-General of the World Health Organisation.
According to global estimates, about 14.3 million infants in 2024 did not receive a single routine vaccine, underscoring persistent gaps in health coverage.
They warned that these gaps are already having consequences, with measles outbreaks rising sharply worldwide, with an estimated 11 million cases reported in 2024.
The number of countries experiencing large outbreaks has nearly tripled since 2021, driven by declining vaccination coverage and, in some areas, growing vaccine hesitancy.
Catherine Russell, Executive Director of UNICEF, said the progress made must be sustained through long-term investment in health systems.
“We’ve reached millions of children who missed vaccines during the pandemic, but many more remain out of reach,” she said.
Similarly, Sania Nishtar, Chief Executive Officer of Gavi, described the initiative as proof of what coordinated global action can achieve.
“This effort shows what is possible when governments, partners, and communities work together to protect the most vulnerable in society,” she said.
Sustaining momentum
As countries mark World Immunisation Week, global health agencies called for renewed commitment to expanding vaccine coverage under the banner “For every generation, vaccines work.”
At the midpoint of the Immunisation Agenda 2030 strategy, they said the priority remains reaching zero-dose children and ensuring equitable access to vaccines, particularly in regions affected by conflict, displacement, and weak health systems.
They emphasised that while large-scale catch-up campaigns can help close gaps, they are resource-intensive and should complement—not replace—routine immunisation services.
“Timely vaccination remains the most reliable way to protect children and prevent outbreaks,” the agencies said, warning that without sustained investment and political will, the gains made in recent years could be reversed.
They emphasised that the success of the Big Catch-Up underscores both the progress achieved and the challenges that remain in ensuring that no child is left behind.
