September 13, 2010
Study Debunks Claims Of Mercury-Based Vaccine Causing Autism
A new study has found that a mercury-based preservative does not increase a child's risk of autism.
The government study shows that kids who have been exposed to thimerosal as babies were no more likely to develop the disorder than those who haven't.
"This study should reassure parents about following the recommended immunization schedule," Dr. Frank Destefano, director of the Immunization Safety Office at the Centers for Disease Control and Prevention (CDC) in Atlanta, and the study's senior author, told Reuters Health.
British physician Andrew Wakefield raised concerns about a link between vaccines and autism about a decade ago.
His study has since been discredited and was retracted earlier this year by the journal that published it. It also sparked a fiercer worldwide debate among scientists and caused many parents to stop getting their children vaccinated.
Outbreaks of measles, mumps and rubella followed after the false report.
According to the CDC, one widespread worry has been that thimerosal may play a key role in the development of autism.
Most scientists believe the condition is a development disorder influenced by genes.
Autism spectrum disorders range from mild Asperger's Syndrome to severe mental retardation and social disability.
CDC researchers used data for U.S. children who were enrolled in one of three managed care organizations and born between 1994 and 1999.
They found 256 children with an autism spectrum disorder, and compared them with 752 children who did not have the condition.
No matter when a child has been exposed to the mercury-based vaccine, there was no increase in the risk of any type of autism spectrum disorder.
The kids who were exposed to the preservative between birth and 20 months of age had slightly lower odds of developing the condition.
"This is a very reassuring study," Dr. Michael J. Smith, a pediatrician at the University of Louisville School of Medicine in Kentucky who was not involved in the research, told Reuters Health.
"These data show that you could receive a thimerosal vaccine and not be concerned about it."
Smith said that autism rates have continued to rise, although thimerosal has been removed from all routine childhood vaccines, except in flu shots.
He said there are alternatives without the preservative, like FluMist, that parents are able to use if they are concerned about thimerosal.
Some parents also worried that giving too many shots at one time could cause mental problems. However, Smith said that studies have dismissed these claims.
"There is no credible evidence" for a link between vaccines and autism, he told Reuters Health.
Autism affects as many as one in 110 U.S. children.
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