Updated at 9:34 a.m. on June 25, 2025 Vaccine experts in the United States have long considered the case on thimerosal closed. A chemical preservative that stamps out contamination in vaccine vials, thimerosal was removed from most U.S. shots more than two decades ago over worries that its mercury content could trigger developmental delays. But those concerns'as well as baseless claims that thimerosal causes autism'have been proved unfounded, many times over. 'We took care of this 20 years ago,' Kathryn Edwards, a pediatrician and vaccine expert at Vanderbilt University, told me. That's not how anti-vaccine activists see the compound. Even the strongest data supporting thimerosal's safety have not quelled the concerns of those who insist on the chemical's harms. And now the CDC's Advisory Committee on Immunization Practices, or ACIP, has signaled that thimerosal's presence in vaccines should remain open for debate. The panel is scheduled on Thursday to discuss the compound, which is...
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