Robert F. Kennedy Jr.’s revamped Advisory Committee on Immunization Practices (ACIP) has struck its first blow against established vaccine practice, recommending against the use of flu shots that contain a preservative that has been used in shots for decades.
While the proposed recommendation affects only a small percentage of flu shots supplied in the U.S., it signals the willingness of the committee to buy into unsubstantiated claims surrounding the negative effects of vaccines. The director of the Centers of Disease Control and Prevention (CDC) typically signs off on ACIP recommendations, but that position is currently unfilled.
The move likely raises alarm bells for those concerned about the influence wielded by RFK Jr., the new secretary of the Department of Health and Human Services (HHS), who has long been an anti-vaccine activist. Earlier this month, RFK Jr. dismissed all 17 members of the ACIP and replaced them with a group of eight advisors, including one who has already stepped down, and others who have expressed their anti-vaccine views.
As for Thursday’s action, the panel came down hard on flu vaccines that contain thimerosal, which is used in multidose vials to prevent contamination after one dose has been drawn. Thimerosal contains trace amounts of mercury. Anti-vaccine activists have claimed that the preservative can cause autism, though multiple studies, including one by the CDC in 2010, have shown that there is no link.
Tracy Beth Hoeg, M.D., Ph.D., of the FDA told the committee that fewer than 5% of the flu vaccines administered in the 2024-25 season contained thimerosal.
Thursday, the ACIP heard a presentation from Lyn Redwood, former president of the anti-vaccine organization Children’s Health Defense, who cited a 2008 University of California, Davis study that can’t be found in public literature. Redwood claimed the study establishes a link between the preservative and the neuroimmune effects that cause autism. A purported author named in the work has distanced himself from any of Redwood's conclusions.
Later Thursday afternoon, the committee supported a move to recommend flu vaccines are provided only in single-dose vials that are free of thimerosal.
The only member of the panel who voted against the measure was Cody Meissner, M.D., of Dartmouth’s Geisel School of Medicine.
“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.”
Another member of the committee, Vicky Pebsworth, Ph.D., abstained from voting because of the way the voting questions were posed.
“We should not be doing anything that restricts access to vaccines of any sort, especially those that are already approved by the FDA and that are already in the schedule,” Pebsworth said.
The ACIP also voted unanimously to reaffirm its recommendation for routine annual influenza vaccination of everyone ages 6 months and older.
After the meeting, the Partnership to Fight Infectious Disease called on RFK Jr. to restore the original ACIP committee and to include the FDA more comprehensively in its process.