The Advisory Committee on Immunization Practices (ACIP), recently reformed by Health and Human Services Secretary Robert F. Kennedy Jr., voted on Thursday in favor of recommending flu shots that do not contain thimerosal, a mercury-based preservative.
This decision is part of a broader set of recommendations aimed at making the 2025-2026 flu season vaccines safer for specific demographics, including children, pregnant women, and adults.
ACIP’s Decision on Thimerosal-Free Flu Shots
The ACIP provides guidance to the Centers for Disease Control and Prevention (CDC) on vaccination policies. The committee voted on four draft recommendations, with three of them addressing the use of thimerosal-free flu vaccines. Specifically, the committee voted:
5-2 in favor of recommending thimerosal-free flu shots for children 18 and under, pregnant women, and all adults. One member voted “no,” and one abstained.
7-0 in favor of recommending thimerosal-free seasonal flu vaccines for people 6 months and older during the 2025-2026 flu season.
What is Thimerosal?
Thimerosal is a mercury-based preservative used in multidose vaccine vials to prevent the growth of bacteria and fungi. Despite concerns raised by anti-vaccine groups, the CDC has consistently stated that there is no link between thimerosal and neurological conditions like autism.
Multiple epidemiological studies have found no connection between thimerosal and autism. In fact, the CDC points out that autism rates have continued to rise even after thimerosal was removed from most childhood vaccines.
Thimerosal-free vaccines are now widely available in the U.S. and are the most commonly administered vaccines. However, thimerosal-containing vaccines are still common in low-income countries due to the lower cost of multidose vials.
Opposition Within ACIP
While most members of the ACIP supported the recommendation for thimerosal-free vaccines, Dr. Cody Meissner, a professor of pediatrics at Dartmouth College, was the sole member to vote “no.”
Meissner, who previously served on the ACIP, strongly disagreed with the claims presented by Lyn Redwood, a former head of the anti-vaccine group Children’s Health Defense, who suggested that thimerosal-containing vaccines were harmful to children.
Meissner pointed out that thimerosal is metabolized into ethylmercury, which is excreted quickly from the body and is not associated with the neurotoxicity of methylmercury (found in fish and shellfish). He argued that the focus on thimerosal was not a significant issue for the ACIP to prioritize.
Abstention and Concerns on Vaccine Access
Vicky Pebsworth, another member of the ACIP, abstained from voting. She expressed concerns over the wording of the question, stating that it conflated two important issues—whether vaccines should be recommended and whether they should contain thimerosal.
She argued that the FDA-approved vaccines should not be restricted, especially since they are already part of the vaccine schedule. Pebsworth emphasized that more discussion should have been had about the implications of restricting access to vaccines.
The Bigger Picture
This vote on thimerosal-free flu shots has broader implications for vaccine policy in the United States. The decision comes at a time when vaccine hesitancy remains an issue, and the CDC’s role in ensuring safe and effective vaccines is constantly under scrutiny.
Despite the scientific consensus around the safety of thimerosal in vaccines, the decision to limit its use in flu shots could have a political and public health impact, particularly in terms of addressing ongoing concerns about vaccine safety.
As flu season approaches, these recommendations will likely influence public opinion, especially among those already cautious about vaccinations.
For now, thimerosal-free vaccines will remain the primary option for flu prevention for most Americans, with ongoing debates about vaccine safety and access continuing to shape the future of public health policy.