The US government has frozen funding to Gavi, the global vaccine alliance, until it commits to phasing out the preservative thimerosal from all vaccines it distributes. The demand stems from claims by US Health and Human Services Secretary Robert F. Kennedy Jr. and his allies that thimerosal, which contains mercury, is linked to autism—a link that remains scientifically unproven.
The US Food and Drug Administration (FDA) has consistently affirmed thimerosal’s safety, noting that it has been widely studied and used effectively to prevent bacterial and fungal contamination in vaccines, causing no adverse effects beyond minor local reactions. The FDA highlighted that a vaccine containing 0.01% thimerosal has roughly the same amount of elemental mercury as a three-ounce can of tuna fish.
Thimerosal is present in about 14% of Gavi’s vaccines, primarily in multi-dose vials used in low- and middle-income countries because they are more cost-effective. These include the pentavalent vaccine, DPT, Tetanus-Reduced Diphtheria (Td), Hepatitis B, Meningococcal A Conjugate (MenA), and Pneumococcal Conjugate Vaccine (PCV). Most vaccines in the US and Europe do not contain thimerosal, as single-dose vials are more common there.
Gavi has responded that it is in contact with the US government regarding the request to remove thimerosal, but any changes to the vaccine portfolio would require approval by Gavi’s Board and be guided by scientific consensus. Pending funds from the Biden administration, amounting to around $300 million, are currently on hold until the matter is resolved.
All vaccines supported by Gavi must be recommended by the World Health Organization’s Strategic Advisory Group of Experts (SAGE) and pre-qualified at each manufacturing site. National Immunisation Technical Advisory Groups (NITAGs) and National Regulatory Authorities (NRAs) in Gavi-supported countries also provide additional approvals, ensuring safety and compliance with international standards.
The dispute follows a broader tension over vaccine safety, with Kennedy asserting last year that the US would withhold funds until public trust was “re-earned,” claiming that Gavi had ignored vaccine safety concerns. As a result of the funding freeze, the US recently lost its seat on Gavi’s board.
