Big Catch-Up delivers 100 million child vaccine doses

GENEVA/NEW YORK — The Big Catch-Up, a historic multiyear, multicountry effort to reverse vaccination declines driven largely by the COVID-19 pandemic, has reached an estimated 18.3 million children ages 1 to 5 across 36 countries with more than 100 million doses of lifesaving vaccines. 

Gavi, the Vaccine Alliance, the World Health Organization, and UNICEF announced the results at the start of World Immunization Week, saying the initiative helped narrow critical immunity gaps among children who missed routine vaccinations during the pandemic.

Of the 18.3 million children reached from 2023 to 2025, an estimated 12.3 million were “zero-dose children” who had not previously received any vaccine.

The initiative also reached 15 million children who had never received a measles vaccine.

The Big Catch-Up delivered 23 million doses of inactivated polio vaccine to unvaccinated and under-vaccinated children, an intervention agencies said is essential to reaching polio eradication.

Program implementation concluded on March 31, 2026, with final data still being compiled.

The global initiative is forecast to be on track to meet its target of reaching at least 21 million unvaccinated and under-immunized children.

However, the agencies warned that while catch-up vaccination is important for closing immunization gaps, routine immunization remains the most effective and sustainable way to protect children and prevent outbreaks of vaccine-preventable diseases.

Beyond pandemic recovery, the Big Catch-Up focused on closing the vaccine equity gap among children who miss essential vaccinations before age 1.

Millions of children miss these vaccines every year, many of them living in fragile, conflict-affected, or underserved communities where they are often not reached as they grow older.

The 36 participating countries across Africa and Asia currently account for 60% of all zero-dose children worldwide.

Pandemic-related immunization disruptions worsened the problem, adding millions more zero-dose children in countries where many already chronically miss vaccines.

To address the issue, the Big Catch-Up went beyond infant immunization by systematically using routine immunization systems to reach older children ages 1 to 5 who remained vulnerable because they missed critical vaccines before age 1.

The initiative helped countries build systems to identify, screen, vaccinate, and monitor coverage among older children, including through updates to age eligibility policies.

Countries also oriented and trained health workers to identify, screen, and vaccinate missed children as part of routine care.

The initiative engaged communities and civil society groups to support catch-up efforts.

By expanding immunization to millions of previously missed children and their communities, the Big Catch-Up helped participating countries improve access to essential health and immunization services in the future.

Among participating countries, Burkina Faso, the Democratic People’s Republic of Korea, Ethiopia, Kenya, Madagascar, Mauritania, Niger, Pakistan, Somalia, Togo, the United Republic of Tanzania, and Zambia reported reaching more than 60% of all zero-dose children under age 5 who had previously missed the first dose of diphtheria, tetanus, and pertussis vaccine, or DTP1.

In Ethiopia, more than 2.5 million previously zero-dose children received DTP1.

Ethiopia also delivered nearly 5 million doses of inactivated polio vaccine and more than 4 million doses of measles vaccine, along with other key vaccines, to unvaccinated and under-vaccinated children.

Countries outside the group also reached large numbers of children.

In Nigeria, 2 million previously zero-dose children were reached with DTP1, while 3.4 million doses of inactivated polio vaccine were administered alongside millions of doses of other vaccines.

The 36 countries received Gavi funding and technical assistance from WHO and UNICEF through the Big Catch-Up.

Many other countries also carried out activities during the same period to accelerate efforts to reach missed children and recover immunization services after pandemic-related backsliding.

“As the largest ever international effort to reach missed children with life-saving vaccines, 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. “Thanks to this accomplishment, not only are millions of children now protected from preventable diseases but so are their communities, for generations to come.”

“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 Dr Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization. “The success of the Big Catch-up is a testament to health workers and national immunisation programmes, which are now better equipped to find and vaccinate children missed by routine services.”

“Vaccinations save lives,” said UNICEF Executive Director Catherine Russell. “This initiative shows what’s possible when countries have the resources, tools, and political will to reach children with lifesaving vaccines. We’ve caught up with some of the children who missed routine vaccinations during the pandemic – but many more remain out of reach. The gains made through the Big Catch-Up must be sustained through investment in strong, reliable immunisation systems, especially at a time where measles is resurging.”

The agencies said the Big Catch-Up marked the first time countries and global partners successfully reached 12.3 million older zero-dose children ages 1 to 5.

Despite the progress, an estimated 14.3 million infants under age 1 globally failed to receive a single vaccine through routine immunization programs in 2024.

Lowering that annual number will require systems that consistently reach the hardest-to-reach communities amid rising birth cohorts, conflict and displacement, funding cuts, and strained health systems.

The consequences of chronic gaps in routine immunization are already visible, the agencies said.

Measles outbreaks are rising in every region, with around 11 million cases in 2024.

The number of countries facing large measles outbreaks has almost tripled since 2021.

The surge has been driven by persistent gaps in measles vaccination through routine immunization programs, compounded by declining vaccine confidence in some previously high-coverage communities.

Large-scale catch-up efforts are resource-intensive and should serve only as a gap-filling measure that complements routine immunization, the agencies said.

Timely vaccination under national immunization schedules provides optimal protection and remains the most sustainable way to safeguard children and communities.