Public Release: 

NNii statement on new thimerosal study

Infectious Diseases Society of America

The following statement can be attributed to Martin G. Myers, MD, executive director of the National Network for Immunization Information (NNii):

This week, the journal Molecular Psychiatry published a study by researchers at Columbia University on the neurotoxic effects on mice of thimerosal, a mercury derivative that has been used as a preservative in vaccines.

The study raises important scientific issues that need to be further explored.

The study found that thimerosal could cause behavioral abnormalities in newborn mice that have a specific genetic susceptibility. However, it is important to keep the study in perspective. Abnormalities were noted only in mice that were specially bred to have problems with their immune systems. How and whether this relates to human infants can only be determined by additional research.

In the meantime, parents should keep two important facts in mind: First, a recent study by the Institute of Medicine found no evidence that children have been harmed by the thimerosal in vaccines. Second, in the United States thimerosal is no longer used as a preservative in most childhood vaccines. (A possible exception is the influenza vaccine, although a thimerosal-free version is available.) Parents who are concerned about mercury can take many steps to reduce their children's exposure without putting their children's health at risk by skipping immunizations--such as getting rid of mercury thermometers or reducing consumption of certain types of fish, such as tuna.

Immunizations have an amazing record of saving children's lives. In fact, immunizations are one of the most effective things parents can do to protect their children from infectious diseases. Given how important immunizations are to children's health, many efforts go into vaccine safety research.


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.

For more information, visit

1. M Hornig, D Chian, W. I. Lipkin. Neurotoxic effects of postnatal thimerosal are mouse strain-dependent. Molecular Psychiatry 2004 Volume 9, advance on line publication

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