Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Brain & Nervous System Health Center

Font Size

Thimerosal: No Smoking Gun

CDC: No Evidence of Child Brain Damage Due to Vaccine Preservative
WebMD Health News
Reviewed by Louise Chang, MD

Sept. 26, 2007 - Thimerosal in vaccines has not affected children's brains or behaviors, the CDC says.

Thimerosal is a mercury-based preservative once common in vaccines. It's now found only in small amounts in some flu vaccines. However, thimerosal was once used in most vaccines given to children.

Although the amounts were tiny, they added up. Because symptoms of autism often appear suddenly around age 1 -- when kids have received a number of vaccinations -- many parents became convinced that thimerosal caused their children's autism. But the Institute of Medicine has twice rejected this idea.

The new CDC study carefully avoided the still-controversial issue of whether thimerosal is linked to autism. A separate CDC study of this issue is under way, with a report expected in a year's time.

"In this study there is nothing you can draw on regarding any relationship to autism," researcher William W. Thompson, PhD, of the CDC's National Immunization Program, said at a news conference.

Instead, the study looked for 42 different neurological and psychological problems in more than 1,000 7- to 10-year-old children exposed to various amounts of thimerosal while still in the womb, from birth to 28 days, or up to age 7 months.

"This was a large, very careful study to determine whether thimerosal exposures in early childhood was associated with bad neuropsychological outcomes," Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said at the news conference. "It came out with very reassuring results."

"Ninety-eight percent of the answers here are very reassuring," John Iskander, MD, MPH, acting director of the CDC's Immunization Safety Office, said at the news conference.

Thimerosal and Tics

What about the other 2% of the study findings? The study looked at 42 different outcomes, ranging from intelligence to fine motor coordination. The researchers performed 378 statistical tests on the data. Each statistical test had 5% odds of being a chance finding.

"By chance alone we would estimate about 5% of test results would be significant," Schuchat said. "And in fact that is exactly what we found: 19, or 5%, of the statistical tests did find significant results. They were pretty evenly split between [linking] better and worse outcomes [to thimerosal]."

1 | 2 | 3

Today on WebMD

nerve damage
Learn how this disease affects the nervous system.
senior woman with lost expression
Know the early warning signs.
woman in art gallery
Tips to stay smart, sharp, and focused.
medical marijuana plant
What is it used for?
senior man
boy hits soccer ball with head
red and white swirl
marijuana plant
brain illustration stroke
nerve damage
Alzheimers Overview
Graphic of number filled head and dna double helix