A study of specially bred mice suggests that a mercury preservative in vaccines could potentially cause some of the brain changes in autism, U.S. researchers said on Wednesday.

The publication of the study gives fuel to an alliance of environmentalists, parents of children with autism, antivaccine advocates and politicians who say they will continue to fight to prove that vaccines can cause autism in susceptible children.

But experts who issued a report last month saying there was no link between vaccines and autism said they had already seen the study and rejected it.

Dr. Mady Hornig of Columbia University in New York said her study shows the possibility that a genetic predisposition could leave certain children vulnerable to a range of toxins in vaccines, including a mercury-based preservative called thimerosal.

Writing in the journal Molecular Psychiatry, Hornig said specially bred mice that have deficient immune systems did show changes in behavior after getting the equivalent of the childhood vaccinations given to U.S. babies and toddlers.

“I think that these findings suggest that it is very plausible that there could be a genetic factor that creates risk for some individuals with autism,” Hornig said in a telephone interview.

INSTITUTE OF MEDICINE REPORT

Hornig presented her findings in February to an Institute of Medicine committee examining the potential link between vaccines and autism.

The institute is an independent body that advises the federal government on health matters.

The committee issued a report last month saying there was no evidence that vaccines or thimerosal could cause autism and advised that research funds looking for the cause of autism would be better spent elsewhere.

Hornig said her research could at the very least be used to reassure parents worried about the safety of vaccines.

Her study was done using a combination of private and federal funds, including money from SafeMinds, a group pursuing the link between all types of mercury and brain disease.

But Dr. Marie McCormick of Harvard University’s School of Public Health, who chaired the panel, said Hornig’s research stretched credibility. For instance, it is not clear that children with autism have impaired immune systems. And the findings from specially bred mice can not be extended to humans.

“Even though she says these behaviors are like autism, it is not clear that these behaviors are analogous to autism,” McCormick added.