Mercury in the flu vaccine. Credit: Shutterstock’s Internal Creative House
The major US health committees voted to phase out thimeromonal, a mercury-based preservative used in several seasonal influenza vaccines.
The vote took place on June 27, 2025 during a meeting of the Advisory Committee on Vaccination Practices (ACIP), the group that guides national vaccine recommendations for the Centers for Disease Control and Prevention (CDC). The committee recommended that all children and adults receive only single-dose influenza vaccines that do not contain thimeromonkeys.
What is thimerosal and why is it debatable?
Thimerosal (spelled as Thiomersal) is an ethyl Mercury-based preservative that has been in use since the 1930s, preventing the growth of large amounts of vaccines from bacteria and fungal growth. According to the CDC, there is a strong safety record.
Most childhood vaccines in the United States have not been thimerosal-free since 2001, but the ingredients remain in some multi-dose influenza vaccines, which account for about 5% of the total dosage.
Despite decades of use and repeated research showing harmful effects, thimerosal has long been a target for anti-vaccine advocates, many of which have linked it to neurological harm and autism.
ACIP’s latest vote was five, one, and one abstain in favor of eliminating thimero monkeys. So why is there a desire to eradicate it?
The panel was recently rebuilt by longtime vaccine critic Robert F. Kennedy Jr. Health Secretary. Kennedy fired all 17 former members in early June and replaced them with eight new members.
Critics argue that the panel’s agenda was influenced by anti-vaccine remarks. The CDC presentation, which is scheduled to review scientific evidence in support of Thimerosal’s safety, was likely discarded, and instead was presented by Lyn Redwood, nurse and founder of the World Mercury Project, a precursor to Kennedy’s child health defense. Her presentation reportedly included at least one untested study.
In response to concerns, panel chair Dr. Martin Kruldorf (former Harvard professor) fired for refusing to the Covid-19 vaccine — “It’s inappropriate to dismiss a presentation just because the person doesn’t have a doctoral degree or MD” ( Guardian).
The only “no” vote for Geisel School of Medicine in Dartmouth, Dr. Cody Maisner, a professor of pediatrics, warned that elimination of thimeromonkeys could limit access to the flu vaccine worldwide.
“The risk of flu is far greater than that from Timelosal, as far as we know,” Maisner said. “I hate people who don’t receive the flu vaccine because the only preparation available contains thimeromonkeys.”Guardian. )
Global implications of faking thimeromonkeys in influenza vaccines
ACIP recommendations only have a direct impact on the US, but are often adopted globally, especially in low-income countries where multi-dose vials are important due to cost and storage constraints.
Thimerosal allows manufacturers to package influenza vaccines into vials serving multiple patients, reducing costs and logistics burdens. Without it, countries may be forced to switch to single-dose formulations. This is more expensive and difficult to distribute.
“We’re supporting our efforts to remove it completely. There are other preservatives that aren’t mercury-based,” said Dr. Jacob Glanville, CEO of San Francisco Biotechnology Company. Fox News).
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