Childhood vaccinations are stagnating, and the threat of future measles and tuberculosis outbreaks is increasing.

Efforts to vaccinate children against deadly diseases are in jeopardy worldwide due to economic inequality, disruptions caused by COVID-19, and anti-vaccine misinformation, a study warned Wednesday. These trends increase the threat of future outbreaks of preventable diseases, while deep cuts in foreign aid threaten previous progress in vaccinating the world's children.

A new study published in The Lancet analyzed childhood vaccination rates in 204 countries and territories. The World Health Organization's (WHO) immunization program is estimated to have saved an estimated 154 million lives over the past 50 years. Vaccination coverage against diseases such as diphtheria, tetanus, whooping cough, measles, polio, and tuberculosis doubled between 1980 and 2023, the international team of researchers found.

However, progress slowed in the 2010s, when measles vaccinations declined in about half of the countries, with the largest decline observed in Latin America. A notable decline of 12% in children vaccinated with a first dose against measles in Argentina.

On the other hand, more than half of all high-income countries saw declines in coverage of at least one vaccine dose. Then the COVID-19 pandemic hit, and routine vaccination services were massively disrupted, resulting in nearly 13 million additional children not receiving any vaccine doses between 2020 and 2023, according to the study.

This disparity persisted, particularly in poorer countries. In 2023, more than half of the world's 15.7 million completely unvaccinated children lived in just eight countries, the majority in sub-Saharan Africa, according to the study.

Brazil is on that list, at the bottom, with 452,000 unvaccinated children. The European Union recorded 10 times more measles cases last year than in 2023. In the United States, a measles outbreak surpassed 1,000 cases in 30 states last month, already more than were recorded in all of 2024. Polio cases, long eradicated in many areas thanks to vaccination, have been on the rise in Pakistan and Afghanistan, while Papua New Guinea is currently experiencing a polio outbreak.

"Routine childhood vaccinations are among the most powerful and cost-effective public health interventions available," said Jonathan Mosser, senior author of the study and a member of the US-based Institute for Health Metrics and Evaluation (IHME).

"But persistent global inequalities, the challenges of the COVID pandemic, and rising misinformation and vaccine hesitancy have all contributed to stalled progress on immunization," she said in a statement. On the other hand, "growing numbers of displaced people and inequalities due to armed conflict, political instability, economic uncertainty, and climate shocks" remain, added Emily Haeuser, lead author of the study, also from IHME.

Researchers warned that these setbacks could threaten the WHO's goal of having 90% of the world's children and adolescents receive essential vaccines by 2030. The WHO also aims to halve the number of children who have not received any vaccine doses by 2030 compared to 2019 levels. So far, only 18 countries have achieved this, according to the study, which was funded by the Gates Foundation and the GAVI vaccine alliance.

The global health community has also been affected by the Trump administration 's decision to drastically reduce U.S. international aid earlier this year. "For the first time in decades, the number of children dying worldwide is likely to increase this year rather than decrease due to massive cuts in foreign aid," Bill Gates said in a separate statement Tuesday.

"That's a tragedy," said the Microsoft co-founder, who pledged $1.6 billion to GAVI, which is holding a fundraising summit in Brussels on Wednesday.