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Timeline: Thimerosal in Vaccines (1999–2008)

The following timeline shows key activities performed by CDC, the U.S. Food and Drug Administration (FDA), the Advisory Committee on Immunization Practices (ACIP), and the Institute of Medicine (IOM) concerning thimerosal in vaccines from 1999 to 2008.


Ongoing. CDC is conducting a thimerosal and autism study in three U.S. managed care organizations to find out if exposure to thimerosal in infancy is related to the development of autism.

Ongoing. A study being completed in Italy compares the prevalence of nervous system disorders among children who were exposed to different amounts of thimerosal in vaccines during infancy.


September 27. A CDC study does not support an association between early exposure to thimerosal in vaccines and nervous system disorders in children between the ages of 7 and 10 years.

July 7. CDC issues a statement on autism and thimerosal that states in part, "Some people believe increased exposure to thimerosal (from the addition of important new vaccines recommended for children) explains the higher prevalence [of autism] in recent years. However, evidence from several studies examining trends in vaccine use and changes in autism frequency does not support such an association."


September 26. In a statement prepared for the Coalition for Mercury-free Drugs, the FDA concludes that the evidence reviewed by the IOM in 2004 does not support an association between thimerosal-containing vaccines and autism.


May 28. ACIP recommends that children between the ages of 6 and 23 months routinely receive an inactivated influenza (flu) vaccine. ACIP does not recommend using the thimerosal-free flu vaccine over the thimerosal-containing flu vaccine, and states that the benefits of flu vaccination outweigh any risk from thimerosal exposure.

May 17. After reviewing scientific studies that examined thimerosal-containing vaccines and autism, IOM concludes in a report that the studies "consistently provided evidence of no association between thimerosal-containing vaccines and autism."


November. A study* finds no consistent significant associations between exposure to thimerosal-containing vaccines and a variety of kidney, nervous system, and developmental problems.

August. Another study looks for a link between autism incidence and the use of thimerosal-containing vaccines. The study does not find a link between thimerosal-containing vaccines and autism in Denmark and Sweden, where autism rates continued to increase although thimerosal was removed from vaccines in 1992.

January. The last children's vaccines that use thimerosal as a preservative expire.


Except for influenza (flu), thimerosal is removed from, or reduced in, all vaccines routinely recommended for children 6 years of age and under manufactured for the U.S. market.

October 1. IOM's Immunization Safety Review Committee issues a report concluding there is not enough evidence to prove or disprove claims that thimerosal in childhood vaccines causes autism, attention deficit hyperactivity disorder, or speech or language delay.

May 5. A risk assessment* of thimerosal use in childhood vaccines finds no evidence of harm from the use of thimerosal as a preservative, other than redness and swelling at the injection site.


June 7 and 8. Fifty-one vaccine and vaccine safety researchers and experts meet at the Simpsonwood Retreat Center in Atlanta, Georgia to review data regarding thimerosal in vaccines and nervous system disorders. A report summarizing the meeting was presented to ACIP.


The FDA reviews the use of thimerosal in childhood vaccines and finds no evidence of harm, but as a precautionary measure, recommends removing thimerosal from vaccines routinely given to infants.

November 5. CDC states that vaccine manufacturers, FDA, and other agencies are working together to reduce the amount of thimerosal in vaccines, or to replace them with thimerosal-free vaccines, as soon as possible.

October 20. ACIP reviews information about thimerosal in vaccines provided by CDC's National Immunization Program and several vaccine manufacturers regarding the availability of vaccines that do not contain thimerosal as a preservative.

July 7. The American Academy of Pediatrics and the Public Health Service issue a joint statement that says, "there are no data or evidence of any harm caused by the level of exposure that some children may have encountered in following the existing immunization schedule." The American Academy of Family Physicians issues a comparable statement soon after.

*Links to non-Federal organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links.

Page last reviewed: September 24, 2008
Page last updated: February 29, 2008
Content source: Immunization Safety Office, Office of the Chief Science Officer

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