The vaccine panel hand-selected by health secretary and anti-vaccine advocate Robert F. Kennedy Jr. on Thursday voted overwhelmingly to drop federal recommendations for seasonal flu shots that contain the ethyl-mercury containing preservative thimerosal. The panel did so after hearing a misleading and cherry-picked presentation from an anti-vaccine activist.
There is extensive data from the last quarter century proving that the antiseptic preservative is safe, with no harms identified beyond slight soreness at the injection site, but none of that data was presented during today's meeting.
The significance of the vote is unclear for now. The vast majority of seasonal influenza vaccines currently used in the US—about 96 percent of flu shots in 2024–2025—do not contain thimerosal. The preservative is only included in multi-dose vials of seasonal flu vaccines, where it prevents the growth of bacteria and fungi potentially introduced as doses are withdrawn.
However, thimerosal is more common elsewhere in the world for various multi-dose vaccine vials, which are cheaper than the single-dose vials more commonly used in the US. If other countries follow the US's lead and abandon thimerosal, it could increase the cost of vaccines in other countries and, in turn, lead to fewer vaccinations.
Broken process
However, it remains unclear what impact today's vote will have—both in the US and abroad. Normally, before voting on any significant changes to vaccine recommendations from the Centers for Disease Control and Prevention, the committee that met today—the CDC's Advisory Committee on Immunization Practices (ACIP)— would go through an exhaustive process. That includes thoroughly reviewing and discussing the extensive safety and efficacy data of the vaccines, the balance of their benefits and harms, equity considerations, and the feasibility and resource implications of their removal.