Over the last 40 years, worldwide access to childhood vaccines has saved more than 150 million lives and lifted tens of millions out of poverty. However, aid organizations still struggle to reach the world’s poorest children, especially those whose countries are ravaged by war and instability.
According to new data from the United Nations, while post COVID-19 immunization numbers continue to rebound, global vaccine coverage remained below pre-pandemic levels. This stagnation in immunization will leave millions of children vulnerable to preventable diseases.
An estimated 13.5 million infants remained unvaccinated last year. While this number is an improvement from 14.2 million “zero-dose” babies in 2024, there is cause for concern.
UNICEF’s global immunization chief, Ephrem Lemango cautioned, “The gains we are celebrating now at this moment are quite fragile” without additional effort and investment. In addition to unvaccinated children, there are many who are under-vaccinated, receiving only one dose of a multi-part regimen. The WHO-UNICEF report shows while 90% of infants worldwide received at least one dose of the diphtheria, tetanus and pertussis (DTP) vaccine last year, only 85% completed the recommended three-dose series.
The Big Catch-Up
To reach children in low- and middle-income countries who missed vaccinations during COVID-19, the World Health Organization, UNICEF and Gavi, the Vaccine Alliance, launched The Big Catch-Up during World Immunization Week in 2023. This multi-country, multi-year initiative, which concluded in March 2026, was on track to close the immunity gap by delivering vaccine doses to 21 million children ages 1 to 5.
The Big Catch-Up trained health workers and used established systems to identify, screen and vaccinate children.
In rural Mozambique, a midwife and nurse vaccinates a child. (Photo via Gavi Facebook)
“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.
Because infants depend on routine clinic visits for immunization, low-income countries where medical access is limited still struggle to afford and distribute enough vaccine doses. Kate O’Brien, the WHO’s director of the Department of Immunization, Vaccines and Biologicals, says, “We are seeing real cracks in the system now for immunization, and we are previewing big risks that are yet to come.”
WHO health workers have reported higher than average outbreaks of measles, diphtheria and cholera over the last year.
Highly contagious, the measles virus acts as a harbinger of vaccination efficacy, revealing immunity gaps in a population. To achieve herd immunity and protect the community from outbreaks, the vaccination rate for measles must be at least 95%. Unfortunately, only 84% of children worldwide received the first dose of the measles vaccine in 2025. Only 77% received the second dose, which makes resistance to the virus more complete.
The WHO estimates that because of under-vaccination, 11 million people likely will contract measles in 2026, most of them in Africa and Asia. Already in 2026, Burundi, Democratic Republic of Congo, Somalia, Sudan and Yemen have experienced an epidemic of measles, a disease for which there is prevention but not treatment.
WHO health workers have reported higher than average outbreaks of measles, diphtheria and cholera over the last year.
Unvaccinated individuals who contract measles, especially patients who are malnourished or lacking access to adequate medical care, are at risk of complications that may result in blindness, deafness and even death. In Bangladesh, which has the world’s highest number of reported measles cases, more than 900 people have died from the virus so far this year.
Gavi
At the center of the struggle to vaccinate the world’s children is Gavi, the Vaccine Alliance. Organized in 2000, Gavi is an independent public-private, multilateral financing mechanism dedicated to supplying and improving access to vaccines, especially for children in the world’s poorest countries. Representatives from the WHO, World Bank, UNICEF and contributing countries sit on the organization’s board. Since its founding, Gavi has helped to immunize 1.2 billion children against 20 diseases, including measles, malaria and polio, thereby preventing 20 million deaths. Gavi also was a partner in COVAX, the worldwide effort to vaccinate residents in low- and middle-income countries against COVID-19.
Under Gavi’s unique cofinancing model, wealthy countries like the US and UK and investors like the Gates Foundation subsidize the cost of vaccines for qualifying low- and middle-income countries who pay what they can afford based on a sliding scale. As the populations of those countries grow and become healthier, they contribute more toward the cost of their vaccines, eventually graduating from Gavi assistance altogether. Thus far, by saving lives and improving health outcomes, Gavi has generated $280 billion in economic benefit for low- and middle-income countries, and 19 of those countries no longer require Gavi assistance to purchase vaccines. Documented progress was being made.
Trump interference
However, in 2025 the United States gutted funding to USAID, which managed the nation’s partnership with Gavi and oversaw the bilateral maternal and child health program that assisted Gavi through immunization campaigns and in-country capacity building. In addition, noted vaccine skeptic and Health and Human Services Secretary Robert F. Kennedy Jr., empowered by Secretary of State Marco Rubio, delayed the $600 million Congress had appropriated for Gavi.
Robert F. Kennedy Jr. (Photo by ALLISON ROBBERT/AFP via Getty Images)
Prior to this, the U.S. had been the entity’s third largest donor, providing 13% of its funding annually since its establishment. Furthermore, the Trump administration’s abandonment of NATO and seeming embrace of Russia compelled the UK, France and several other wealthy countries to redirect portions of their international aid toward defense spending. That combined decrease in donations left Gavi with a significant budget shortfall, compounding the difficulty of immunizing the world’s most vulnerable children.
Thankfully, despite these significant challenges, there are signs of hope on the horizon for expanding global vaccine coverage. Newly chosen UK Prime Minister Andy Burnham has pledged to return the nation’s international funding levels to 0.7% of Gross National Income, a percentage enshrined into law in 2015 but subsequently reduced by his predecessors. In May, a bipartisan group of senators led by Susan Collins, R-Maine, and Patty Murray, D-Wash., with support from Mitch McConnell, R-Ky., Lisa Murkowski, D-Alaska, Brian Schatz, D-Hawaii, and Jeanne Shaheen, D-N.H., sent a letter to the State Department inquiring about the appropriated Gavi funding. On July 29, 2026, the administration relented and said it would “immediately release” the $600 million, which will expire Sept. 30. Without this funding, 75 million children would not receive their routine immunizations and an estimated 1.2 million of them would die as a result. But the road ahead remains steep.
In exchange for releasing the $600 million, Kennedy is demanding Gavi phase out vaccines that use mercury-based thimerosal under the mistaken belief that this preservative causes autism. Scientific studies reviewed by the American Academy of Pediatrics and the European Medicines Agency have repeatedly shown thimerosal is a safe ingredient.
When multiple doses of vaccine are drawn from the same vial, which is often the case in global health settings, thimerosal destroys any contaminating bacteria or fungi entering the vial with each new needle. Switching to the thimerosal-free vaccine used in the US and Europe, which is designed for single-dose distribution and is therefore more difficult to transport and refrigerate, will be an added expense for Gavi. The Trump administration also prevented Gavi from sharing any US funds with its core partner the WHO. Trump signed EO 14155 withdrawing the US from the WHO in 2025, and this was made final in January 2026.
The president also issued an executive order revising childhood vaccine recommendations in the US, but aid workers have no plans to follow this new schedule. Even so, there is the risk that this executive order will sow confusion and cause parents around the globe to question the safety of vaccines.
Tarik Jašarević, WHO spokesperson, told a press briefing in Geneva that countries’ vaccine schedule recommendations are best determined by independent experts and must be “free of industry and political influence.”
Past successes prove reinvesting in international aid can and should reverse stagnating vaccine rates. Only time will tell if this money will be enough to overcome the misinformation propagated by the Trump administration and online influencers. The world may need a second Big Catch-Up.
Kristen Thomason is a freelance writer and journalist living outside Edinburgh in the United Kingdom. She has produced educational and promotional media for national and international religious organizations and public television. Kristen also worked with local churches in Metro D.C. and Toronto, Canada. With a master’s degree in communication and undergraduate degrees in media studies and classics, she is interested in the intersection of politics, religion, history and the arts.
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