Study: No increased autism risk from mercury-based perservative in vaccines

Exposing a fetus or young infant to vaccines with the mercury-based preservative called thimerosal does not increase the risk for autism, according to a study published Monday in the journal Pediatrics.

"This study adds to the evidence that thimerosal-containing vaccines do not increase a child's risk of developing autism," lead study author, Dr. Frank DeStefano of the Centers for Disease Control and Prevention (CDC) tells CNN.

Researchers studied the medical records of 256 children diagnosed with autism and 752 typically developed children born between January 1994 and December 1999. The children were between 6 and 13 years old when the medical data was reviewed – 85 percent of them were boys. The research concluded that there was no evidence that children exposed to the mercury in the vaccines were at risk for getting autism.

According to the CDC, an average of 1 in 110 children in the United States have some form of autism and boys are 4 to 5 times more likely to have autism than girls.

In 2004 the Institute of Medicine reviewed existing research regarding a possible link between vaccines and autism and concluded "that the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism."

Still several advocacy groups and many parents believe vaccines caused their children's autism.

Earlier this year, a federal court set up by Congress to decide claims over vaccine safety, ruled scientific evidence presented did not establish a link between thimerosal in vaccines and autism.

Dr. Geraldine Dawson, Chief Science Officer for the advocacy group Autism Speaks calls the study in Pediatrics significant because it found higher levels of thimerosal exposure were not linked to a higher risk for autism. "One study can't answer all questions, but this study adds to a large body of evidence indicating that early thimerosal exposure through vaccination does not cause autism." She adds, "we encourage parents to have their children vaccinated and to establish a trusting relationship with their child's pediatrician so they can discuss any concerns they have."

Dr. Paul Offit, Director of the Vaccine Education Center at the Children's Hospital of Philadelphia, has long argued that there is no connection. He writes about how believing in this connection can put children at risk in his book "Autism's False Prophets." Offit says "this is at least the 6th study done on thimerosal - they've all shown the same thing. There's not a relationship between thimerosal and autism." Offit suggests it's time to move on and focus on other possible causes of autism.