UNITED NATIONS - Immunization efforts are under growing threat as funding cuts and humanitarian crises jeopardize progress over the past five decades and leave millions of people at risk, multiple world agencies warned Thursday.

In a joint statement, the World Health Organization, the United Nations Children's Fund (UNICEF) and Gavi, a global vaccine alliance, said that outbreaks of vaccine-preventable diseases, such as measles, meningitis, and yellow fever, are rising globally. Some diseases like diphtheria, which have long been held at bay or virtually disappeared in many countries, are at risk of re-emerging.

Data shows measles cases reached an estimated 10.3 million in 2023, a 20 percent increase compared to 2022. The agencies warned that this upward trend likely continued into 2025, as outbreaks have intensified around the world.

In the past 12 months, 138 countries have reported measles cases, with 61 experiencing large or disruptive outbreaks, the highest number recorded in any 12-month period since 2019.

Meningitis cases in Africa also rose sharply in 2024. In the first three months of this year, more than 5,500 suspected cases and nearly 300 deaths were reported in 22 countries.

Funding cuts have worsened the outbreak response and immunization services, especially in the most vulnerable countries, the agencies said.

A WHO study finds nearly half of low- and lower-middle-income countries are facing moderate to severe disruptions to vaccination campaigns, routine immunization, and access to supplies due to reduced donor funding.

"Vaccines have saved more than 150 million lives over the past five decades," said Tedros Adhanom Ghebreyesus, the WHO director-general. "Funding cuts to global health have put these hard-won gains in jeopardy."

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The agencies called for urgent and sustained political attention and investment to strengthen immunization programs and protect significant progress achieved over the past 50 years.