{"id":1483,"date":"2025-06-28T15:35:18","date_gmt":"2025-06-28T15:35:18","guid":{"rendered":"https:\/\/pronews.in\/index.php\/2025\/06\/28\/what-is-thimerosal-vaccine-preservative-called-toxic-by-us-health-chief\/"},"modified":"2025-06-28T15:35:18","modified_gmt":"2025-06-28T15:35:18","slug":"what-is-thimerosal-vaccine-preservative-called-toxic-by-us-health-chief","status":"publish","type":"post","link":"https:\/\/pronews.in\/index.php\/2025\/06\/28\/what-is-thimerosal-vaccine-preservative-called-toxic-by-us-health-chief\/","title":{"rendered":"What is Thimerosal, vaccine preservative called \u2018toxic\u2019 by US health chief?"},"content":{"rendered":"
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During the first meeting of Health and Human Services Secretary Robert F Kennedy Jr\u2019s<\/a> recently downsized vaccine panel, the group voted to stop recommending flu vaccines containing thimerosal, a vaccine preservative.<\/p>\n

In a lengthy June 24 X post that preceded the meeting, Kennedy, who spent two decades as an anti-vaccine movement leader, described thimerosal using terms such as \u201ctoxic\u201d and said hundreds of studies identify it as a carcinogenic \u201cpotent neurotoxin\u201d. He also said there are high doses of mercury in flu shots recommended to pregnant women and children.<\/p>\n

The US Centers for Disease Control and Prevention\u2019s Advisory Committee on Immunisation Practices\u2019 (ACIP) two-day meeting on June 25 and 26 included discussion of vaccines containing thimerosal before its vote on flu vaccines.<\/p>\n

ACIP is an independent group which provides vaccine recommendations the CDC director reviews and decides whether to formally adopt. Earlier in June, Kennedy dismissed<\/a>\u00a017 ACIP members, replacing them with seven new members,\u00a0including\u00a0people who\u2019ve\u00a0expressed doubt about vaccine efficacy\u00a0and\u00a0promoted anti-vaccine falsehoods<\/a>.<\/p>\n

Doctors and scientists who study vaccines have been researching thimerosal\u2019s use for decades. Here\u2019s what we know about the vaccine preservative and its removal from flu vaccines.<\/p>\n

\"flu
A nurse prepares a flu shot from a vaccine vial at the Salvation Army in Atlanta, February 7, 2018 [File: David Goldman\/AP]<\/figcaption><\/figure>\n

What is thimerosal?\u00a0<\/strong><\/h2>\n

Thimerosal is a mercury-based preservative used in some vaccines.<\/p>\n

Many people \u2013 particularly those who are pregnant or breastfeeding \u2013 encounter warnings about consuming mercury, such as in seafood. But those warnings are about methylmercury, which is found in certain kinds of fish and is known to be toxic to people when consumed at high levels.<\/p>\n

Thimerosal contains ethylmercury \u2013 a single-letter difference that might not sound significant, but is.<\/p>\n

Human bodies can break down and excrete ethylmercury quickly, meaning it is\u00a0less likely\u00a0to cause harm. By contrast, methylmercury is more likely to\u00a0accumulate\u00a0in the body and cause harm.<\/p>\n

In vaccines, thimerosal is added to\u00a0prevent harmful microbes\u00a0such as bacteria and fungi from\u00a0growing in vaccine vials.<\/p>\n

\u201cIntroduction of bacteria and fungi has the potential to occur when a syringe needle enters a vial as a vaccine is being prepared for administration,\u201d the\u00a0CDC\u2019s website\u00a0said. \u201cContamination by germs in a vaccine could cause severe local reactions, serious illness or death. In some vaccines, preservatives, including thimerosal, are added during the manufacturing process to prevent germ growth.\u201d<\/p>\n

Thimerosal has been at the heart of Kennedy\u2019s anti-vaccine activism<\/a> for 20 years.<\/p>\n

In 2005, Kennedy wrote an article co-published by Rolling Stone and Salon that alleged leading health agencies including the CDC and US Food and Drug Administration had colluded with vaccine manufacturers to conceal a study that found thimerosal \u201cmay have caused autism in thousands of kids\u201d. Scientists and researchers said Kennedy\u2019s argument was inaccurate and misleading. Continued research has found no link between thimerosal and autism. Kennedy\u2019s article was removed from Rolling Stone, and Salon retracted it in 2011.<\/p>\n

In 2015, Kennedy wrote a book opposing thimerosal\u2019s use in vaccines.<\/p>\n

Which vaccines use thimerosal?\u00a0<\/strong><\/h2>\n

Thimerosal is not used in the vast majority of vaccines.<\/p>\n

All vaccines the CDC routinely recommends for children age six or younger are available without thimerosal.<\/p>\n

Children receiving the routine paediatric vaccine schedule \u201ccan get completely immunised without any thimerosal-containing vaccines\u201d, said Dr Mark Sawyer, a paediatrics professor at the University of California San Diego School of Medicine and a paediatric infectious disease physician.<\/p>\n

Some childhood vaccines\u00a0have never contained\u00a0thimerosal. These include the measles<\/a>, mumps and rubella \u2013 or MMR \u2013 vaccine<\/a>, the varicella or chickenpox vaccine, the inactivated polio vaccine<\/a> and the pneumococcal conjugate vaccine.<\/p>\n

Thimerosal was\u00a0removed\u00a0from most vaccines \u2013 including all childhood vaccines \u2013 as of 2001, the CDC\u00a0said.<\/p>\n

Thimerosal is still used in vaccines today, but not as widely.<\/p>\n

The preservative is in only a small fraction of influenza vaccine vials, specifically the multi-dose vials that constitute a small portion of the US flu shot supply, Dr Jake Scott told PolitiFact. Scott is a Stanford University School of Medicine infectious disease specialist.<\/p>\n

The FDA said\u00a0thimerosal use has declined\u00a0as vaccine manufacturers have developed more single-dose vaccines that do not require preservatives.<\/p>\n

Scott said the CDC lists 12 influenza vaccine formulations for the 2024 to 2025 flu season, which will also cover the 2025 to 2026 season because no new flu vaccines have been licensed. Of those 12 vaccines,\u00a0just three\u00a0are multi-dose vaccines that contain thimerosal at 25 micrograms \u2013 equal to 25 millionths of a gram \u2013 per dose, he said.<\/p>\n

CDC\u2019s supply data shows single-dose, thimerosal-free syringes make up about 96 percent of the US flu vaccine supply, leaving roughly 4 percent as multi-dose vials, Scott said.<\/p>\n

\u201cSingle-dose syringes are the default for paediatrics and prenatal care, so real-world exposure is even lower,\u201d he said.<\/p>\n

Because flu vaccines with thimerosal constitute a small portion of the influenza vaccine supply, public health experts told\u00a0The Washington Post the committee\u2019s vote to stop recommending them would have a limited impact, although it could make flu shots more expensive and less accessible in some parts of the US.<\/p>\n

What does research show about thimerosal?<\/strong><\/h2>\n

Because anti-vaccine activists\u2019 focus has centred on whether thimerosal causes autism, numerous scientific studies have investigated a potential link and found no causal relationship between the preservative and autism.<\/p>\n

When scientists evaluated thimerosal\u2019s potential impacts and risks they found:<\/p>\n