Sept. 13, 2010 -- Exposure to thimerosal-containing vaccines in infancy or in the womb is not associated with an increased risk for developing autism, according to a new study from the CDC.

Children in the study who developed autism spectrum disorder (ASD) actually had less exposure to vaccines with the mercury-containing preservative than children who developed normally.

The study is the latest of almost 20 studies to find no link between childhood vaccinations and autism.

It comes seven months after the first study that linked vaccines and autism -- conducted 12 years ago -- was retracted by the journal The Lancet. The U.K. doctor who published the study was banned from practicing medicine.

Cases of autism continue to rise throughout the world. The CDC now estimates that as many as one in 110 children in the U.S. develop ASD, which includes a range of developmental disorders from Asperger’s syndrome to severe retardation and almost total social isolation.

CDC Director of Immunization Safety and study researcher Frank DeStefano, MD, MPH, tells WebMD that while the reason some children develop ASD remains a mystery, the focus should now shift to other potential causes.

“I don’t think there is much worthwhile to study anymore with regard to thimerosal-containing vaccines and autism,” he says.