4 things to know about the thimerosal of the vaccine ingredient

The federal government could quickly recommend that people only receive flu shots without an ingredient called Thimerosal.

The preservative has been absent in most flu vaccines for almost two decades, but was in the agenda of a committee that advises the Centers for Disease Control and Prevention on Vaccin Policy.

The meeting in June was the first since earlier in the month, when health secretary Robert F. Kennedy Jr. All 17 earlier members of the Advisory Committee for Immunization Practices or Acip fired and installed his own Lei van Zeven.

Thimerosal has been a target of groups that question the safety of vaccine. That despite “a long record of safe and effective use” as a vaccine conservatory, according to the Food and Drug Administration.

In three separate voices, ACIP ordered that children, pregnant women and all adults receive a single dose of flu immunisations with vaccines that do not contain thimerosal. The next step would be a decision by Kennedy or the CDC on the recommendations.

“It is as if they made this meeting to solve a problem that no longer really exists,” says Dr. Jesse GoodmanA former chief scientist at FDA who is now at Georgetown University.

The only member of the committee to vote against the recommendations was Dr. Cody MeissnerA professor in pediatrics at Dartmouth College.

“Of all the problems that ACIP needs to be focused, this is not a major problem,” he said. “The risk of influenza is so much greater than the non-existent, as far as we know, the risk of Thimerosal.”

He added: “There is no scientific evidence that Thimerosal has caused a problem.”

But what is Thimerosal and what would happen if it was effectively banned from flu shots? Here are four things to know.

1. It is a preservative that contains mercury

Thimerosal is a chemical connection that is about 50% mercury due to weight, According to the FDAAnd has been used in trace amounts since the 1930s as a preservative in vaccines and medicines.

The connection is used in bottles with multiple doses of the flu vaccine. It is the task to prevent the bottle from being polluted between patients and possibly someone becomes sick, says Dr. Michelle FiscusChief Clinical Officer of the Association of Immunization Managers.

“If you constantly go in and out of the bottle to prepare a new dose, you run the risk of getting bacteria or fungus in that bottle,” says Fiscus. “And we don’t want those vaccines to be infected.”

She says that although most flu vaccines come in a single dose today, the multi-use vials are cheaper and take less space in cooking. So for some health centers they are more practical.

“When we enter the flu season, it is not uncommon to get all your flu vaccine in advance at the start of the season. And sometimes storage in the fridge can be a problem,” says Fiscus.

Yet they are not common. According to to the CDC94% of flu shots in the 2024-25 season was Thimerosal-free or thimerosal-saving.

2. Thimerosal has not been used often since 2001

In 1997, the FDA Modernization Act required the government to evaluate Kwik in Kinder vaccines.

But the heavy metal comes in various forms. Methylkwik is the connection found in seafood that is not easy to break down and can be toxic. Ethylmercury, the form in Thimerosal, has another risk profile.

“It made no distinction between that kind of mercury and ethylmercury, a form of mercury that is managed very quickly by the body and is eliminated by the kidneys,” says Fiscus. “And Ethylmercury is where Thimerosal is derived.”

Thimerosal was removed from most vaccines from childhood in 2001, although there was no evidence that it caused damage to the recipients of Vaccin, says Fiscus.

3. It has a discredit connection to autism

Concern that vaccines cause autism has arisen with a 1998 study from 1998 by Dr. Andrew Wakefield, which focused on the MMR vaccine against measles, mumps and rubella. Wakefield lost his medical license and The BMJ, A prominent medical magazine, called it an “extensive fraud” in An editorial 2011.

Nevertheless, speculation about a connection between vaccines and autism – once defended by Kennedy itself – Continued and expanded with Thimerosal, although a link to autism has been repeatedly refuted.

A Report from 2004 Published by the National Academies of Sciences Engineering and Medicine repeated that Thimerosal was not associated with autism. Next Studies in 2006, 2007, 2009 and 2010 According to the CDC, Thimerosal did not show associated with autism or neurophysiological problems.

Moreover, Georgetown’s goodman points out that, despite the removal of Thimerosal from most vaccines, autism rates have continued to rise in the last 20 years, “which would certainly not be consistent with something to do with youth vaccines.”

4. Most people will not notice whether Thimerosal is no longer recommended in Schoten

Because most flu shots are administered with spraying with one dose, most people probably don’t notice this fall and winter if the CDC decides to effectively ban Thimerosal, Fiscus says.

Nevertheless, a thimerosal prohibition can result in some challenges, because health centers start ordering flu vaccines for the next flu season in February. It is possible that manufacturers have to exchange them.

Sanofi, which makes multidosis bottles of a vaccine called Fluzone and Single dose spraying, says that only contains a “very small number” of his doses of Thimerosal. “We acknowledge the recommendation of the new ACIP. We are now waiting for the CDC’s decision on the path. We will have sufficient delivery of Sanofi Flu vaccine to support the customer’s preference for this season.”

Seqirus, the other company that makes multidosis vials from flu vaccine with Thimerosal, said in a statement to NPR that they “represent a very small part” of his total vaccine offer. “We are committed to supporting our customers in completely switching to spraying with one dose and do not expect any consequences for our delivery or shipping stiming this season.”

The committee’s process can be a sign of the coming things

Fiscus, from the Association of Immunization Managers, says that the Commission’s decision to only recommend Single-Dose Flu Shots without Thimerosal, it appears that it is willing to make a decision without following the protocol and considering scientific evidence.

“Will this be the standard now?” She says. “That is very worrying or that is where this is going.”

Goodman is also worried that these movements will ultimately undermine confidence in vaccines in the United States and abroad.

“One of my real worries is that although the flu vaccines are not perfect, they save lives. If they are given, they are still underented,” he says. “If it is more difficult to access or offer them, people would be injured at the end of the day.”