In a sweeping move to eliminate mercury exposure from vaccines, U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr. has formally banned thimerosal, a mercury-based preservative long used in flu shots administered to children and pregnant women. The decision follows a June vote by the newly appointed CDC Advisory Committee on Immunization Practices recommending a full ban on mercury-containing preservatives in all vaccines.
Thimerosal’s active ingredient, ethyl mercury, has been recognized as a potent neurotoxin. “Until we withdrew the recommendation last week, flu shots containing thimerosal, astonishingly, were still being administered to millions of Americans, including pregnant women and children,” Kennedy stated.
The ban ends over two decades of federal inaction, despite warnings from scientists, peer-reviewed research, and internal government findings about the risks of mercury exposure. Kennedy cited a long trail of evidence, including studies from the National Library of Medicine and the National Toxicology Program, that identify thimerosal as not only a neurotoxin, but also a carcinogen, mutagen, and endocrine disruptor.
Kennedy criticized both regulatory agencies and the pharmaceutical industry for allowing thimerosal to remain in use. “In early 2001, the director of the FDA Office of Vaccine Research and Review, the late William Egan, admitted under oath before Congress [that] thimerosal safety had never been studied in human beings,” he said. The CDC, he noted, had no guidelines for safe ethyl mercury exposure.
Government documents and industry disclosures have long acknowledged thimerosal’s dangers. Its own label warned against use during pregnancy and cited mutation risks in mammals. Material Safety Data Sheets (MSDS) list toxic effects on the nervous and reproductive systems, and note potential for “mild to severe mental retardation and mild to severe motor coordination impairment” in exposed children.
The California EPA and the U.S. EPA have both identified thimerosal and ethyl mercury as reproductive toxins. According to Kennedy, the amount of ethyl mercury in a single flu shot was “25,000 times [the] EPA safety level for drinking water.” When expired, such vaccines are classified as hazardous waste and must be disposed of in special landfills.
Despite repeated warnings, federal agencies failed to act. “Why were we injecting this toxin into babies and pregnant women?” Kennedy asked. He cited a 2000 study by the National Research Council that found prenatal and infant mercury exposure disrupted brain development by interfering with neuron division and migration.
A 2005 NIH study—commissioned by the FDA—found ethyl mercury crosses the blood-brain barrier and lodges in the brain, converting into the most toxic form of mercury at twice the rate of methyl mercury found in fish. Follow-up research showed the mercury can remain in brain tissue for over 27 years.
In 2017, a CDC study linked miscarriage to flu shots, finding the odds of miscarriage within 28 days were 7.7 times higher among pregnant women who received the vaccine. That same year, a Journal of the American Medical Association study linked first-trimester flu shots with an elevated risk of autism spectrum disorders. “Instead of immediately withdrawing thimerosal from flu shots to protect women and their babies, CDC issued a gag order instructing its personnel not to discuss that study,” Kennedy said.
A 2001 report from the Institute of Medicine concluded that the connection between thimerosal and neurological injuries, including autism, is “biologically plausible.” The report also recommended ending the use of mercury-preserved vaccines.
Kennedy acknowledged longstanding resistance from the pharmaceutical industry and some media outlets. “For 20 years, I’ve been battling to get mercury out of vaccines,” he said. “Instead of following the science, CDC and its allies in the industry and the pharma-funded media have marginalized, vilified, and censored parents, doctors, and scientists who question the wisdom of using mercury in vaccines by calling them by the pejorative ‘anti-vaxxer’.”
He compared the situation to his earlier environmental advocacy: “I’ve been trying to get mercury out of fish for four years, and nobody called me ‘anti-fish’.”
Kennedy said the pattern of regulators ignoring science to protect profits is ending. “Companies protect profits by suppressing the science, and regulators lie to the public and look the other way. But this pattern ends now under President Trump’s new HHS.”
While thimerosal has been eliminated, Kennedy emphasized that flu vaccines will still be available. Manufacturers have confirmed they can replace multi-dose vials (which required preservatives like thimerosal) with single-dose applications. This ensures continued access for both the Vaccines for Children program and adult immunization efforts.
“This change ensures the uninterrupted supply,” he said.
Kennedy urged international health organizations to follow the U.S. lead. “We urge the World Health Organization and GAVI to stop their programs of injecting mercury into more than 100 million Black and Brown babies in developing countries annually.”
He called the U.S. decision “a major step toward restoring public trust in the safety of our medicines” and said it “sends a clear message: The days of ignoring the science are over. The days of putting profits ahead of people are over.”
Kennedy closed by reaffirming his agency’s new direction: “We are remaking FDA and CDC under President Trump’s leadership… into the vigilant public watchdogs that they were always meant to be.”