NNii Media Advisory about NEJM’s Article on Thimerosal Exposure and Neuropsychological Outcomes


Diana Olson - (703) 299-0201

September 26, 2007

The article by Thompson and colleagues, Early Thimerosal Exposure and Neuropsychological Outcomes at 7 to 10 Years, published this week in the New England Journal of Medicine, should reassure parents who received immune globulin during pregnancy or whose children received thimerosal-containing vaccines as infants.

Although multiple studies around the world have found no causal link between thimerosal and autism, more studies have been needed regarding other possible neuropsychological outcomes. For example, a 2003 study suggested that thimerosal might have been associated with tics and speech or language delay at one HMO—but no such associations were found in two other HMOs.

  • This new study looked for signs of other (non-autistic) neuropsychological outcomes in 1,047 children born between 1993 and 1998 who were exposed to thimerosal in vaccines and immune globulins they received prior to birth and/or as infants.
  • The study found that groups of children who had been exposed to increasing amounts of thimerosal all had very similar developmental outcomes. The few significant associations that were observed were almost equally divided between better and poorer outcomes, suggesting that the observed associations were chance findings.

As was the case with autism and thimerosal, the accumulating evidence shows no association between thimerosal exposure in infancy and the subsequent development of other neuropsychological abnormalities.

Some other points to remember:

  • Immunization remains one of the most important things parents can do to protect their children from serious infectious diseases. 
  • There is no evidence that links vaccines and autism. This conclusion is now based on well-established scientific studies conducted by independent investigators, in multiple locations, and who examined large numbers of children.
  • There has been no thimerosal preservative in US-licensed vaccines given to children less than 6 months of age since early 2003—the amount was greatly reduced by 2001. There is no evidence that there has been a reduction of cases of autism since thimerosal was removed from vaccines administered to children less than 6 months of age.
  • With no scientific evidence that thimerosal preservative in vaccines causes harm (except rare allergic reactions), many other countries continue to utilize thimerosal preservative-containing vaccines to be able to safely administer vaccines using multiple dose vials.
  • The only vaccine routinely recommended for administration to US children that may contain thimerosal preservative is trivalent inactivated influenza vaccine (TIV). TIV is not administered to children less than 6 months of age because they have a poor immune response to this vaccine. TIV is also available without thimerosal preservative.

The NNii media office has scientific experts available to discuss these issues. Contact Diana Olson at (703) 299 0201 to schedule an interview.

  • For more information, visit for non-technical but evidence-based information about this and related topics.

The National Network for Immunization Information (NNii) provides up-to-date, science based information about immunizations to health professionals, the public, policymakers, and the media. NNii is based at the University of Texas Medical Branch in Galveston and is affiliated with the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, the American Academy of Pediatrics, the American Nurses Association, the American Academy of Family Physicians, the National Association of Pediatric Nurse Practitioners, and the American College of Obstetricians and Gynecologists, the Society for Adolescent Medicine and the American Medical Association.