In the first gathering of Health and Human Services Secretary Robert F. Kennedy Jr.’s newly trimmed vaccine panel, the members voted against recommending flu vaccines that include thimerosal, a common preservative.
Ahead of the meeting, Kennedy shared a detailed post on June 24, labeling thimerosal as “toxic” and asserting that numerous studies categorize it as a carcinogenic “potent neurotoxin.” He expressed concern about the levels of mercury present in flu shots suggested for pregnant women and children.
The U.S. Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) held a two-day meeting on June 25 and 26 that discussed vaccines containing thimerosal prior to the vote on flu shots.
ACIP is an independent body that makes vaccine recommendations for the CDC director to consider for formal adoption. Earlier in June, Kennedy removed 17 previous ACIP members, replacing them with seven individuals who have raised doubts about vaccine effectiveness and promoted various antivaccine narratives.
Thimerosal has been a focal point of Kennedy’s antivaccine stance for two decades, and extensive research has been conducted on its use in vaccines. Here’s a closer look at thimerosal and its role.
What is thimerosal?
Thimerosal is a mercury-based preservative found in some vaccines.
Warnings about mercury consumption, especially in seafood, reach many, particularly pregnant or breastfeeding individuals. However, these warnings pertain to methylmercury, known for its toxic effects at high levels.
Thimerosal, on the other hand, contains ethylmercury, which is processed and eliminated from the body much more effectively.
Ethylmercury is less likely to cause harm compared to methylmercury, which tends to accumulate and can be more dangerous. Thimerosal helps prevent harmful microbes, such as bacteria and fungi, from growing in vaccine vials.
It’s crucial because when a syringe enters a vial, there’s a chance for contamination, which could lead to serious reactions or illness. Thimerosal prevents such microbial growth during the manufacturing of vaccines.
For 20 years, Kennedy has been vocal about his concerns regarding thimerosal.
In 2005, he published an article claiming that major health agencies conspired to hide evidence linking thimerosal to autism. However, scientists have consistently refuted this claim, finding no credible evidence linking thimerosal to autism. Over the years, various publications have retracted or removed Kennedy’s assertions.
Which vaccines include thimerosal?
Most vaccines do not contain thimerosal.
All vaccines recommended by the CDC for children ages six and under are available without thimerosal. Children can be fully immunized without receiving any thimerosal-containing vaccines.
Some childhood vaccines, such as the MMR, chickenpox, and polio vaccines, have never included thimerosal. By 2001, thimerosal was largely eliminated from vaccines, particularly those given to children.
Today, thimerosal is found in a limited number of flu vaccine vials, mainly in multi-dose vials that represent only a small portion of the U.S. flu vaccine supply. The FDA has noted a decline in thimerosal use as manufacturers create more single-dose vaccines that do not require preservatives.
For the upcoming flu seasons, only three out of 12 influenza vaccine formulations are multi-dose and contain thimerosal at a low concentration.
Public health experts indicated that the recent voting decision may have limited consequences, although it might affect the availability and cost of flu shots in certain areas.
What does research say about thimerosal?
Research has focused primarily on potential connections to autism, but numerous scientific studies have found no evidence proving a causal link.
Experts have concluded that thimerosal was primarily removed from vaccines as a precautionary measure, rather than due to any findings proving it was unsafe. Ongoing studies have indicated that thimerosal hasn’t shown any harm to individuals.
