SHERIDAN, WYOMING – July 25, 2025 – In a significant move reshaping national vaccine policy, the U.S. Department of Health and Human Services (HHS) has announced it will eliminate thimerosal from all influenza vaccines distributed in the United States. The decision follows a unanimous vote by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) on June 26, 2025, and marks the end of an era for a preservative that has been both a practical necessity and a source of public debate for over two decades.
Strategic impact on manufacturers and supply chain
While thimerosal is currently used in only about 4% of flu vaccines—mainly multi-dose vials—the HHS ruling will require vaccine manufacturers to fully transition to thimerosal-free production. This includes replacing the final few thimerosal-containing products, namely two from Seqirus and one from Sanofi Pasteur, according to CDC data.
The HHS clarified in its announcement that the shift is not expected to disrupt flu vaccine supply chains, noting that existing manufacturing capabilities and alternative preservatives should support uninterrupted vaccine availability.
Balancing safety concerns with logistical realities
Thimerosal, a mercury-based compound used to prevent microbial growth in multi-dose vials, has long been a point of contention. Its use has allowed for mass immunization in resource-limited and rural settings, offering critical logistical advantages. However, opponents have drawn attention to its mercury content, specifically ethylmercury, and have linked its use—without scientific basis—to autism and other health concerns.
“After more than two decades of delay, this action fulfills a long-overdue promise to protect our most vulnerable populations from unnecessary mercury exposure,” stated HHS Secretary Robert F. Kennedy Jr. in the official release.
The CDC maintains that thimerosal is safe and has no association with neurodevelopmental disorders. “There is a robust body of peer-reviewed, scientific studies . . . that support the safety of thimerosal-containing vaccines. The scientific evidence collected over the past 20+ years does not show any evidence of harm, including serious neurodevelopmental disorders, from use of thimerosal in vaccines,” the agency reiterated in its ongoing guidance.
Industry concerns over equitable vaccine access
Despite the phase-out, some experts within the immunization community voiced concerns about potential unintended consequences—particularly reduced vaccine access in underserved regions. ACIP member Cody Meissner noted, “My concern is that by insisting that vaccine doses not contain thimerosal, that might lower vaccine access. The risk from the flu is so much higher than [from] thimerosal, I would hate for someone not to receive the vaccine because it does contain thimerosal.”
Nonetheless, HHS emphasized that the availability of mercury-free alternatives and increasing production of single-dose vials will mitigate access issues, ensuring continuity in immunization efforts nationwide.
Aligning policy with public perception and global trends
The final phase-out aligns U.S. policy with global public health trends that increasingly favor mercury-free vaccine formulations. While science has consistently demonstrated the safety of thimerosal, public perception and regulatory caution have driven a gradual shift away from its use since the FDA’s 1999 guidance recommending its removal from pediatric vaccines.
“Injecting any amount of mercury into children when safe, mercury-free alternatives exist defies common sense and public health responsibility,” Kennedy added. “Today, we put safety first.”
Looking ahead
The HHS decision signals the conclusion of a longstanding debate and reinforces a national commitment to vaccine safety and public confidence. With production adaptations already underway, stakeholders across the pharmaceutical supply chain are expected to align with the updated directive ahead of the upcoming flu season.
Learn more at www.hhs.gov