At the first meeting of the recent downsized vaccine panel for Health and Human Services Secretary Robert F. Kennedy Jr., the group voted to suspend recommendations for influenza vaccines, including the vaccine preservative, thimerosal.
Kennedy, who spent 20 years as an anti-vaccine movement leader in the long X-mail on June 24, preceded the conference, described thimeromonkeys using terms such as “toxicity,” said hundreds of studies identify as a carcinogenic “strong neurotoxin.” He also said there was a large amount of mercury in the flu shots recommended for pregnant women and children.
The two-day meeting of the US Disease Control and Prevention Advisory Committee (ACIP) on June 25th and 26th included discussions on vaccines, including thimeromonkeys, before voting for the influenza vaccine.
ACIP is an independent group that provides vaccine recommendations that are reviewed by CDC directors and that determine whether to adopt them formally. At the beginning of June, Kennedy dismissed 17 ACIP members, expressing doubts about the vaccine’s effectiveness and replaced them with seven new members, including those who promoted anti-vaccine falsehoods.
Doctors and scientists studying the vaccine have been studying the use of thimeromonal for decades. Here’s what we know about vaccine preservatives and removal from flu vaccines:
What is thimero monkey?
Thimerosal is a mercury-based preservative used in some vaccines.
Many people, especially pregnant or breastfeeding people, come across warnings about the consumption of mercury, such as seafood. However, these warnings concern methylmercury found in certain types of fish, and are known to be toxic to people when consumed at high levels.
Thimerosal contains Ethylmercury. This may not be important, but it is.
The human body can break and be excreted. This means that it is less likely to cause harm. In contrast, methylmercury accumulates in the body and is more likely to cause harm.
The vaccine adds thimeromonkeys to prevent harmful microorganisms such as bacteria and fungi from growing in vaccine vials.
“The introduction of bacteria and fungi can occur when the needle of the syringe enters the vial, as the vaccine is prepared for administration for administration,” the CDC website states. “Contamination by bacteria in a vaccine can cause severe local reactions, serious illness or death. With some vaccines, preservatives containing timerosal are added to prevent reproductive growth during the manufacturing process.”
Thimeromonkeys have been at the heart of Kennedy’s anti-vaccine activity for 20 years.
In 2005, Kennedy wrote an article co-published by Rolling Stone and Salon. This has concealed research that major health agencies, including the CDC and the U.S. Food and Drug Administration, colluded with vaccine manufacturers to “produce autism in thousands of children.” Scientists and researchers said Kennedy’s argument was inaccurate and misleading. Continued studies did not have a link between thimeromonkeys and autism. Kennedy’s article was removed from Rolling Stone, and the salon retracted in 2011.
In 2015, Kennedy wrote a book against the use of thimeromonkeys in vaccines.
Which vaccines use thimerosal?
Thimeromonkeys are not used in most vaccines.
All vaccines that the CDC recommends routinely are available to children under the age of 6 without thimeromonkeys.
Dr. Mark Sawyer, a pediatric infectious disease professor at the University of California, San Diego School of Medicine and a pediatric infectious disease doctor, says that children who receive a daily pediatric vaccine schedule can “be fully vaccinated without a vaccine containing thimeromonkeys.”
Some pediatric vaccines do not contain thimeromonkeys. These include measles, mumps, or MMR vaccines, water cell or chicken pox vaccines, inactivated polio vaccines, and pneumococcal conjugated vaccines.
According to the CDC, as of 2001, thimerosal was removed from most vaccines, including all pediatric vaccines.
Thimerosal is still used in vaccines today, but it is not very wide.
Preservatives are just a small portion of the large vials that make up a small portion of the flu vaccine vials, particularly the US flu shot supply. Scott is an infectious disease expert at Stanford University School of Medicine.
The FDA said the use of thimerosal has been reduced as vaccine manufacturers developed more single-dose vaccines that do not require preservatives.
Scott said the CDC lists 12 influenza vaccine formulations for the 2024-2025 flu season. Of these 12 vaccines, only three are multi-dose vaccines that contain thimeromonas at 25 micrograms, equivalent to one in 25 million grams per dose, he said.
CDC supply data show single-dose thimerosal-free syringes, accounting for about 96% of the US influenza vaccine supply, leaving around 4% as multidose vials.
“Single projectiles are the default for pediatric and prenatal care, so real-world exposure is even lower,” he said.
Because flu shots with thimeromonkeys form a small part of the supply of flu vaccines, public health experts told the Washington Post that a committee vote to stop the recommendations could make flu shots more expensive and more accessible, but in some parts of the United States, flu shots are more expensive and more accessible.
What does research on Thimerosal show?
As the focus of anti-vaccine activists is on whether thimerosal causes autism, many scientific studies have investigated the potential links and found no causal relationship between preservatives and autism.
When scientists assessed the potential impact and risk of thimeromonal, they found:
The vaccine containing thimeromonkeys “does not appear to increase mercury levels above the infant’s safe levels.” Three controlled, two uncontrolled observational studies “provided consistently unrelated evidence” between vaccines containing thimeromonal and autism. “There is no scientific evidence that vaccines containing thimeromonal are responsible for adverse events among children born to women who received the influenza vaccine during pregnancy.”
Vaccine researchers told Politifact that thimeromonkeys were removed from the vaccine due to a wealth of caution, not because thimeromonkeys proved unsafe.
Rachel Roper, a professor of microbiology and immunology at East Carolina University, thought it could cause problems, so thimeromonkeys were removed from the vaccine. But in the end, “study was done and showed it to be safe.”
There is no evidence before that Thimerosal “causing any harm,” Sawyer said.
