HHS Secretary RFK Jr. Removes Thimerosal Preservative from Flu Vaccines

As of July 23, 2025, Department of Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. has signed a Centers for Disease Control and Prevention (CDC) advisory committee recommendation to remove thimerosal from all US-distributed influenza vaccines.1

Only 1 dissenting vote was placed during the Advisory Committee on Immunization Practices (ACIP), from Cody Meissner, MD, Geisel School of Medicine, Dartmouth.1

“The risk from influenza is so much greater than the non-existent—as far as we know—risk from thimerosal,” Meissner said. “I would hate for a person not to receive the influenza vaccine because the only available preparation contains thimerosal. I find that very hard to justify.”1

Thimerosal is a compound containing ethyl mercury, which has been used as a preservative in multidose vials of influenza vaccines. The compound, introduced in the 1930s as a method of preventing bacterial and fungal contamination of vaccines, has been the subject of some controversy over the last decade.2

In 1999, the US Food and Drug Administration (FDA) determined the childhood immunization schedule may expose adolescents and infants to higher levels of mercury than recommended by the Environmental Protection Agency. Since this decision, thimerosal has been removed from all routine childhood vaccines save for influenza.2

In 2014, an article posited that thimerosal had been found harmful in over 165 studies, highlighting death, acrodynia, mercury poisoning, allergic reaction, autoimmune reaction, malformations, Well’s syndrome, developmental delay, and neurodevelopmental disorders such as tics, language delay, and attention deficit disorder.3 However, these findings have been refuted in numerous subsequent studies, including 1 from the CDC in 2010 and another more recently published in 2017 that indicated no link between thimerosal and adverse outcomes like autism or abnormal neuropsychological functioning.2,4 Overall, annual exposure to thimerosal through influenza vaccinations is widely considered safe.2

The 2017 article further cited the flawed article connecting autism to the measles, mumps, and rubella (MMR) vaccine, which has caused widespread parental concern despite being rejected as fraud. However, the spurious findings persist in causing fewer children to receive standard vaccinations for common diseases. Additionally, this falsified connection has been extrapolated to vaccines in general, with a sizeable amount of the population believing in a connection between developmental challenges and vaccines.2

“After more than 2 decades of delay, this action fulfills a long-overdue promise to protect our most vulnerable populations from unnecessary mercury exposure,” RFK Jr. said in a press release. “Injecting any amount of mercury into children when safe, mercury-free alternatives exist defies common sense and public health responsibility. Today, we put safety first.”1

Sanofi and CSL Seqirus, the 2 companies whose influenza vaccines still contain thimerosal, have acknowledged and responded to the decision. Both companies provide more flu shots in single-dose syringes, which do not contain thimerosal, than multidose vials, as announced in 2 separate press releases.1

“We acknowledge the recommendation of the new [ACIP],” a spokesperson for Sanofi said in a statement to FIERCEPharma. “We will have sufficient supply of Sanofi flu vaccine to support customer preference for this season.”1

References

1. Dunleavy K. RFK Jr. rubber-stamps ACIP recommendation to remove thimerosal from all vaccines in US. FIERCE Pharma. July 23, 2025. Accessed July 24, 2025. https://www.fiercepharma.com/pharma/rfk-jr-rubber-stamps-adcomm-recommendation-remove-thimerosal-all-vaccines

2. Spencer JP, Trondsen Pawlowski RH, Thomas S. Vaccine Adverse Events: Separating Myth from Reality. Am Fam Physician. 2017;95(12):786-794. https://www.aafp.org/pubs/afp/issues/2017/0615/p786.html

3. Hooker B, Kern J, Geier D, et al. Methodological issues and evidence of malfeasance in research purporting to show thimerosal in vaccines is safe. Biomed Res Int. 2014;2014:247218. doi:10.1155/2014/247218

4. US Center for Disease Control. CDC Study (2010) on Thimerosal and Risk of Autism. Last reviewed August 24, 2020. Accessed July 24, 2025. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/vaccinesafety/concerns/thimerosal/study-risk-autism.html