A recent decision by a federal vaccine advisory panel, which was recently reshuffled by health secretary Robert F. Kennedy Jr., recommended that flu vaccines containing the preservative thimerosal should not be administered to Americans. This recommendation came after three votes related to safety concerns raised by new panel members, despite previous studies over the past 25 years indicating no significant issues with thimerosal.
In practical terms, the impact of this decision on Americans is expected to be minimal, as only a small percentage of flu vaccine doses in the U.S. market contain thimerosal. Approximately 4% of flu doses are packaged in multi-dose vials with thimerosal to reduce the risk of contamination during the withdrawal of doses.
However, this move is seen as a victory for Kennedy, a vocal critic of vaccines, who has used his position to address the concerns of the anti-vaccine community. Experts caution that this decision could raise doubts about the safety of flu vaccines and vaccines in general, potentially leading to further declines in vaccine uptake.
Flu vaccine uptake has already decreased since the Covid-19 pandemic, with less than half of eligible Americans receiving a flu shot in the previous winter. The percentages for children, pregnant individuals, and adults were also below desired levels, according to the Centers for Disease Control and Prevention.
Kennedy recently replaced all 17 members of the Advisory Committee on Immunization Practices (ACIP) with new members lacking expertise in vaccines. During a recent two-day meeting, concerns were raised about the high number of pediatric deaths during the 2024-2025 flu season, with some members downplaying the severity of the situation.
While the sole pediatrician on the panel, Cody Meissner, opposed the recommendation to use only thimerosal-free flu vaccines, citing scientific evidence of its safety, other members voted in favor. The new committee’s decisions must still be approved by the CDC director or the health secretary to become policy.
Thimerosal has not been used in pediatric vaccines for over 20 years, as a precautionary measure following concerns about a possible link to autism. Despite no evidence supporting this link, thimerosal was phased out of pediatric vaccines.
During the panel meeting, a former president of an anti-vaccine group presented outdated studies questioning the safety of thimerosal, despite rebuttals from the CDC. The lack of CDC input in the discussion raised concerns among liaison members participating in the meeting.
Overall, the decision to recommend against thimerosal-containing flu vaccines may have limited practical implications but could fuel skepticism about vaccine safety. Future discussions within the committee are expected to address these concerns and ensure evidence-based recommendations are made.
