U.S. Health and Human Services Secretary Robert F. Kennedy Jr. on 23 July formally banned the use of thimerosal in all influenza vaccines distributed nationwide, adopting a recommendation issued last month by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices. The committee, whose seven current members were appointed by Kennedy after he dismissed the previous 17, voted 5-1 on 26 June to advise that Americans receive only thimerosal-free flu shots. The panel’s lone pediatrician opposed the measure, citing a lack of evidence that the mercury-based preservative poses a health risk. Thimerosal has been largely phased out of U.S. vaccines for more than two decades and was present in only about 4–5 percent of flu doses last season. The Food and Drug Administration and CDC say extensive studies show no harm from the low levels once used, but anti-vaccine advocates have long claimed a link to autism and other disorders. HHS said vaccine makers can meet demand with single-dose, preservative-free formulations and that supplies should not be interrupted. Companies such as GlaxoSmithKline, Sanofi and CSL, which still package some multi-dose thimerosal-containing vials, face higher costs as they shift production. Kennedy has not yet acted on two other ACIP votes, including the committee’s routine recommendation that everyone aged six months and older receive an annual flu shot. The CDC director’s post remains vacant, underscoring the unusual step of the HHS secretary signing vaccine policy directly and highlighting his broader effort to remake federal immunization guidelines.