(WASHINGTON) — The Advisory Committee on Immunization Practices (ACIP), made up of members recently hand-selected by Health and Human Services Secretary Robert F. Kennedy Jr., voted 5-1 on Thursday to recommend against flu vaccines containing the preservative thimerosal.
A few moments before, the Centers for Disease Control and Prevention’s vaccine advisory committee voted 6-0 to recommend all Americans aged 6 months and older receive an annual influenza vaccine.
One committee member, Vicky Pebsworth, abstained on each vote.
Thimerosal is a mercury-based preservative, which is used to prevent microbial contamination of vaccines. Most flu vaccines currently used in the United States contain little to no thimerosal, but both the Food and Drug Administration and the CDC say there is no evidence low doses of thimerosal in vaccines cause harm other than minor reactions at the injection site, such as redness or swelling.
Additionally, a 2010 CDC study found exposure to vaccines and immunoglobulins that contain thimerosal, in prenatal or infant stages, does not increase risk for autism spectrum disorder.
This preservative was previously used in some common childhood immunizations, However, in the late 1990s, federal health agencies, the American Academy of Pediatrics and vaccine manufacturers agreed to reduce or eliminate thimerosal in vaccines as a precautionary measure, which public health experts previously told ABC News gave rise to anti-vaccine groups alleging thimerosal is not safe and fueled speculation that mercury causes autism.
Kennedy, who has promoted vaccine-skeptic views that experts and decades of robust research have refuted, wrote a book in 2014 falsely claiming thimerosal is “toxic to brain tissue” and may cause autism, calling for its removal from all vaccines.
During the ACIP meeting, Lyn Redwood, a former president of Children’s Health Defense, a group that used to be chaired by Kennedy, gave a highly charged presentation as a private citizen. She claimed the preservative was toxic to the brain and refuted evidence-based claims that there has been no proven harm from thimerosal in vaccines.
Her presentation received pushback from ACIP member Dr. Cody Meissner, who was the only member to vote against the recommendation. He said there “is no scientific evidence that thimerosal has caused problems.”
“The risk for influenza is so much greater than the non-existing risk from thimerosal,” he added.
Meissner said vaccines with thimerosal are metabolized as ethylmercury, not methylmercury, which is the form of mercury found in fish and shellfish, and is known to be a neurotoxin.
“I’m not quite sure how to respond to this presentation,” he said. “This is an old issue that has been addressed in the past. Ethylmercury is excreted much more quickly from the body. It is not associated with the high neurotoxicity that methylmercury [is].”
Meissner also added that thimerosal is included in most multi-dose vaccines administered around the world because single-dose vials are more expensive, and removing thimerosal could increase the costs of vaccines.
“Thimerosal is included in most vaccines that are administered around the globe, and that is because single-dose vials are more expensive, and many countries cannot afford a single-dose vial,” Meissner said.
He went on, “I realize ACIP is focused on the United States, but the recommendations that the ACIP makes are followed among many countries around the world and removing thimerosal from all vaccines that are used in other countries, for example, is going to reduce access to these vaccines, it will increase cost.”
Multiple liaisons of medical groups in the committee also questioned in the meeting why Redwood was permitted to present given her limited scientific background and pushed back on the lack of peer-reviewed studies in her presentation.
“This committee has always prided itself on openness, transparency and data and evidence. So I am wondering if we will have an actual scientific presentation with peer-reviewed literature, strong evidence to actually discuss this issue, as many statements have been made here today, without support of science or evidence, but merely opinion,” Dr. Jason Goldman, a liaison for the American College of Physicians (ACP), said in the meeting.
A CDC review of evidence on thimerosal was previously published on the agency’s website — showing no safety risks from the ingredient — but was later taken down. A former CDC official posted a copy of the article online.
“A scientifically rigorous CDC report reviewing the safety of thimerosal was posted for public access and then abruptly removed at the direction of the Office of the Secretary. The removal of this document, which contextualized decades of evidence showing no link between thimerosal and neurotoxicity or autism, raises serious concerns about transparency and the integrity of the decision-making process,” Sean O’Leary, chair of the American Academy of Pediatrics’ Committee on Infectious Diseases, said in a statement to ABC News.
Doctors have voiced concern that no longer recommending thimerosal in some flu shots could lead to less people getting vaccinated and fuel further distrust of vaccines.
“Any decrease in the number of flu vaccines available will likely result in fewer people being vaccinated and subsequently more hospitalizations and deaths. Its removal could also signal to the general public unwarranted safety concerns,” O’Leary said.
Another heated exchange in the meeting came during the discussion of flu vaccines when ACIP member Dr. Robert Malone described the 250 flu deaths among children during the most recent flu season as a “modest number.”
“The 250 pediatric deaths, which is, let’s acknowledge, is a modest number fortunately,” Malone said.
This past season saw the highest number of flu deaths among children for a non-pandemic season, and the highest number seen since the 2009 H1N1 global flu pandemic, CDC data shows.
Malone received immediate push back during the meeting. Goldman from ACP said the number of deaths “is not a small number, especially if it’s your own child dying from the vaccine preventable illness.”
Copyright © 2025, ABC Audio. All rights reserved.
