The CDC's newly rebuilt Advisory Committee on Immunization Practices (ACIP) took aim Thursday at a mercury-based preservative long targeted by vaccine skeptics, recommending that children, pregnant women, and all other adults use only single-dose seasonal influenza vaccines without thimerosal.

Taking aim at a longtime target of anti-vaccine activists, CDC advisors said Thursday that the U.S. should not administer influenza vaccines containing thimerosal, a mercury-based preservative used to protect multi-dose vials of vaccine.

Robert F. Kennedy Jr.’s revamped Advisory Committee on Immunization Practices 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.