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Vaccines Do Not Cause Autism 


A November 2002 article in the NY Times magazine renewed interest in the false hypothesis that vaccines could be linked to autism.  Neal Halsey, MD, Professor of International Health and Pediatrics and Director of the Institute for Vaccine Safety at the Johns Hopkins University, does not believe that thimerosal causes autism in children.  Dr. Halsey expressed concern about subtle learning disabilities from exposure to mercury from environmental sources and possibly from thimerosal when it was used in multiple vaccines.  However, this should not have been interpreted as support for theories that vaccines cause autism, a far more severe and complex disorder. Dr. Halsey submitted a letter to the editor of the New York Times to correct the misinterpretation of his opinion; the editors decided to print a short correction instead.

Dr. Halsey's concern about thimerosal had to do with early brain development delays - not with autism.  In 1999, he realized that the combined amount of thimerosal in the recommended vaccines could expose infants and children to more ethylmercury than the maximum recommended level.   


In an effort to make vaccines as safe as possible, Dr. Halsey worked with the American Academy of Pediatrics and the US Public Health Service to urge reductions in exposure of infants and children to mercury in all forms and to discontinue using thimerosal as a preservative whenever possible. Today, the vaccines routinely administered to infants and young children in the United States do not contain thimerosal as a preservative.

click for more information on thimerosal


Recent media on this issue:


  • New York Times Magazine article (Nov 10, 2001) - Misleading title and photo captions and incorrect statements led many to misinterpret Dr. Halsey's opinion on thimerosal and autism.


  • National Public Radio interview (Nov 11, 2002) - Dr. Halsey, in his interview with John Hamilton on Morning Edition, made clear his belief that thimerosal does not cause autism.


  • Diane Rehm Show interview (Nov 13, 2002) - Dr. Halsey appeared on this NPR radio show to clarify his position on thimerosal..


  • New York Times correction (Nov 15, 2002) -

    An article and a subheading in The Times Magazine on Sunday about the possibility of a link between brain development in children and thimerosal, a preservative formerly used in vaccines, misstated the views of Dr. Neal Halsey, a Johns Hopkins researcher. Dr. Halsey says that when he described thimerosal injury as a possibility that "must be addressed," he was referring to developmental delay, not to autism. Thus the subheading under the title "The Not-So-Crackpot Autism Theory" erred in saying of a possible autism link that Dr. Halsey "thinks it's an issue worth investigating."


  • Letter to the Editor of the New York Times (sent November 11 - NYT declined to publish in favor of the above correction)


    This page was last updated on October 18, 2017

    2016 Institute for Vaccine Safety