Autism cases in California continued to climb even after a mercury-rich vaccine preservative that some people blame for the neurological disorder was removed from routine childhood shots, a new study found.
Researchers from the state Department of Public Health found the autism rate in children rose continuously during the 12-year study period from 1995 to 2007. The preservative thimerosal hasn't been used in childhood vaccines since 2001, but is used in some flu shots.
Doctors say the latest study adds to existing evidence refuting a link between thimerosal exposure and autism risk and should reassure parents that the disorder is not caused by vaccinations. If there was a risk, they said, autism rates should have dropped between 2004 and 2007.
The findings show "no evidence of mercury poisoning in autism" since there was no decline in autism rates even after the elimination of thimerosal, said Dr. Eric Fombonne, an autism researcher at Montreal Children's Hospital who had no role in the research.
Some advocacy groups blame thimerosal for the impaired social interaction typical of autism. Nearly 5,000 claims alleging a vaccine-autism link have been lodged with the U.S. government, which is deciding whether victims should receive compensation from a government fund.
Dr. Daniel Geschwind, a neurologist at the David Geffen School of Medicine at the University of California, Los Angeles, said the focus now should be on exploring the causes of autism such as possible genetic links.
"Something else must be at play and we need to know what that is if we're really serious about preventing autism," said Geschwind, who had no connection with the study.
For their study, California public health officials calculated the autism rate by analyzing a database of state-funded centres that care for people with autism and other developmental disorders. ...