The Conversation An expert committee that advises the Centers for Disease Control and Prevention voted on June 26, 2025, to cease recommending the use of a mercury-based chemical called thimerosal in flu vaccines. Only a small number of flu vaccines – ones that are produced in multi-dose vials – currently contain thimerosal.
Thimerosal is almost never used in vaccines anymore, but vaccine skeptics have falsely claimed it carries health risks to the brain. Public health experts have raised concerns that the committee’s action against thimerosal may shake public trust and sow confusion about the safety of vaccines.
The committee, called the Advisory Committee on Immunization Practices, or ACIP, was meeting for the first time since Health Secretary Robert F. Kennedy Jr. abruptly replaced its 17 members with eight handpicked ones on June 11.