The Trump administration has demanded that Gavi phase out thimerosal in vaccines to receive future U.S. funding. A U.S. official and a Gavi spokesperson confirmed this to Reuters. As a result, this marks a major shift in U.S. global health policy.
The move reflects long-standing claims by anti-vaccine groups. Notably, Robert F. Kennedy Jr., the U.S. Health Secretary, leads one such group. For years, they have claimed that thimerosal in vaccines causes autism. However, decades of research show no link. In fact, the World Health Organization (WHO) and other experts agree: thimerosal is safe.
In June 2025, Kennedy cut $300 million in annual U.S. funding to Gavi. He justified this by citing unproven safety concerns. Now, the U.S. Department of Health and Human Services says it will withhold all new funding. Specifically, this includes both pending Biden-era pledges and future contributions. The condition is clear: Gavi must create and start a plan to remove thimerosal in vaccines.
A U.S. official claimed Gavi has refused to draft such a plan. On the other hand, Gavi acknowledged the request but stressed that science must guide decisions. “We hope to welcome the U.S. back as a donor,” a spokesperson said. “Nevertheless, any change to our vaccine portfolio requires board approval and scientific review.”
Thimerosal prevents contamination in multi-dose vials. Importantly, these vials are common in low- and middle-income countries. Because they are cheaper and easier to ship than single-dose options, they help reach more children. Consequently, removing thimerosal could raise costs and reduce access. Ultimately, millions of children might miss life-saving shots.
Wealthy nations like the U.S. and Canada rarely use multi-dose vials. This is because their systems favor single-use formats. Even so, they still allow thimerosal when needed. Under Kennedy’s leadership, the U.S. stopped using flu vaccines with thimerosal—about 5% of its supply. Yet, federal agencies had long deemed them safe.
Now, the U.S. argues Gavi should match policies in rich countries. But this ignores real-world challenges in poorer regions. According to the WHO, the benefits of vaccination far outweigh any theoretical risk from thimerosal. After all, deadly diseases like measles and diphtheria pose far greater threats.
The funding freeze is already hurting Gavi. Previously, the U.S. provided 13% of its budget. Combined with cuts from other donors, Gavi now faces serious shortfalls. Therefore, it has started cost-cutting measures that may delay vital programs.
At the same time, the Trump administration is reshaping global health. Indeed, it has left the WHO and slashed billions in aid. Instead, it now favors bilateral deals over multilateral partnerships. Recently, the CDC funded a hepatitis B study in Guinea-Bissau. However, that study now faces ethical review after the CDC reversed its newborn vaccine recommendation.
Experts warn that politicizing thimerosal in vaccines erodes public trust. Moreover, it puts global health at risk. With vaccine-preventable diseases on the rise, decisions must rely on evidence—not ideology.
