No Link Between Mercury in Vaccines, Autism
Researchers who studied three decades' worth of Denmark's national data on autism found no correlation with thimerosal, a mercury-based compound used as a preservative in vaccines, and the incidence of the neurological disorder.
Many parents of autistic children have fingered the mercury in childhood vaccines as the cause of the severe developmental disorder. Mercury can cause neurological damage in high doses, Reuters reported.
The researchers set out to test that contention, reviewing the data on 956 children diagnosed as autistic between 1971 and 2000 and comparing that to the widespread use of thimerosal in state innoculation programs.
They reported that the incidence of autism began to increase from 1991, and continued even among children who were born after 1992 when thimerosal-containing vaccines were discontinued.
"Our ecological data do not support correlation between thimerosal-containing vaccines and the incidence of autism," wrote the authors in the September issue of the journal Pediatrics.
They further suggested that the sharp increase in autism cases seen in Denmark during the 1990s "may be attributable to more attention being drawn to the syndrome of autism and to a change in the diagnostic criteria," in 1994.
Autism undermines a child's ability to connect with the world, and predominantly afflicts boys.
Autistic children often have difficulty making eye contact and carrying on a conversation, and many engage in ritualistic behavior such as hand-flapping and following routines.
There is no known cause and no cure.
Most experts believe there is a genetic component to autism. But some researchers and parents suspect that an unknown environmental factor -- such as a toxin, pesticides or a bad reaction to a vaccine -- may trigger autism in genetically vulnerable children.
U.S. public health officials decided that thimerosal should be removed from vaccines as a precautionary measure in 1999.