US Freezes Gavi Funding Over Mercury Preservative in Vaccines

The Trump administration has frozen hundreds of millions of dollars in funding to Gavi, the Vaccine Alliance, demanding the organization phase out vaccines containing thimerosal, a mercury-based preservative widely used in developing nations. The move marks an unprecedented shift in US vaccine policy and threatens to disrupt vaccination programs across the world's poorest countries.

The freeze affects $300 million in funding approved by Congress in 2024 under the Biden administration, as well as any future US contributions. A spokesperson for the Department of Health and Human Services said the United States will not release these funds or provide new money until Gavi develops and begins implementing a plan to remove thimerosal from its vaccine portfolio.

Background

Thimerosal has been used as a preservative in multidose vaccine vials since the 1930s to prevent bacterial and fungal contamination. The compound contains ethylmercury, a form of mercury that the human body can excrete. While the preservative is no longer used in routinely administered vaccines in the United States, Canada, and most European countries, it remains common in multidose vaccines distributed to lower-income nations.

Gavi, established in 2000 by the World Health Organization, World Bank, UNICEF, and the Gates Foundation, has vaccinated more than 1.2 billion children across 78 countries and prevented more than 20 million deaths from diseases like measles and pneumonia. The United States has been a major financial supporter, contributing more than $8 billion since 2001.

The Biden administration pledged $1.6 billion to Gavi over five years in 2024. However, when the Trump administration took office, it announced plans to terminate funding for the organization entirely.

Key Details

The funding freeze comes after Robert F. Kennedy Jr., who leads the Department of Health and Human Services, cut $300 million in annual funding to Gavi in June 2025. Kennedy has long promoted concerns about vaccine safety that contradict scientific evidence. He told Gavi leaders in a pre-recorded video that the organization had neglected vaccine safety issues in its drive to promote universal vaccination.

"In its zeal to promote universal vaccination, it has neglected the key issue of vaccine safety," Kennedy said in the video sent to Gavi officials. "When the science was inconvenient, Gavi ignored the science."

An HHS spokesperson told Reuters that the United States requested Gavi submit a detailed action plan with a timeline for phasing out thimerosal-containing vaccines. The official said the request aims to bring Gavi's policies in line with standards in the US, Canada, and most European nations. Gavi has not yet developed such a plan, according to the HHS statement.

Why This Matters for Poor Countries

Multidose vaccines are particularly important for low-resource countries because they cost significantly less than single-dose vials and require simpler cold-chain logistics for storage and distribution. Switching to single-dose vaccines or finding alternative preservatives would require major changes throughout the entire manufacturing, supply, and delivery pipeline.

Gavin Yamey, a professor of global health and public policy at Duke University, called the demand baseless and warned it would cause significant disruption. Over two decades of research has shown thimerosal is safe at the levels used in vaccines, he noted. The World Health Organization has also concluded that the small amount of thimerosal in multidose vaccines does not cause harm.

"It would cause enormous upheaval and could not be done suddenly, as it would require huge changes to the entire pipeline from manufacturing to supply and delivery, and there would need to be studies conducted of the safety and efficacy of using a different preservative," Yamey told health policy reporters.

Yamey argued that children in low- and middle-income countries would suffer the most from the policy, as vaccination programs could face delays or shortages during any transition period.

What This Means

The freeze represents a significant departure from decades of US support for global vaccination efforts. Congress approved $300 million for Gavi in the current foreign assistance appropriations bill, though the measure still requires Senate approval and the president's signature. The current congressional bill includes the funding, but its fate remains uncertain.

Gavi's board, which once included US representation, no longer has an American member because of the stalled funding situation. A Gavi spokesperson said any decision about thimerosal would require approval from the organization's 28-member board and input from governance committees, guided by scientific consensus.

The demand has no basis in scientific data or evidence, according to health experts. Thimerosal contains ethylmercury, which differs from methylmercury, the toxic form of mercury. The controversy around thimerosal stems from concerns raised in the 1990s about mercury exposure in vaccines, but extensive research has found no harm from the preservative at the levels used.

Meanwhile, the freeze threatens to disrupt vaccination campaigns in some of the world's poorest nations at a time when measles, diphtheria, and other preventable diseases remain serious threats to children's health. Gavi remains in contact with the US government on the matter but has not indicated whether it will comply with the demand.