Vaccine Preservative Linked To Brain DisordersFeb 5, 2004 | www.ctv.ca A new study is linking an additive used in the flu vaccine to an increased possibility of developing neurological disorders, such as autism and ADHD, attention deficit-hyperactivity disorder.
The flu vaccine contains an additive called thimerosal, a mercury-based preservative. The chemical has been shown to interfere with brain development.
Thimerosal was phased out of the vaccines generally given to children in Canada since the 1960s. Yet it is still in the flu vaccine, says CTV medical correspondent Avis Favaro.
"It's always been in the flu vaccine," she says. "But it's only lately that the flu vaccine has been recommended to children six months and older."
The American university researchers looked at how thimerosal affects brain growth in children. They found that exposure to heavy metals, including ethylmercury-containing thimerosal, interrupts growth factor signaling in cells, causing adverse effects in regulating DNA function and brain development.
"Scientists certainly acknowledge that exposure to neurotoxins like ethanol and heavy metals can cause developmental disorders," said lead researcher Dr. Richard Deth. "But until now, the precise mechanisms underlying their toxicity have not been known.
Deth says his study could account for the rising rates of autism in recent decades, when more thimerosal-containing shots were added to a child's vaccine schedule.
"The recent increase in the incidence of autism led us to speculate that environmental exposures, including vaccine additives might contribute to the triggering of this disorder."
Favaro says the study shouldn't cause parents to panic or to stop vaccinating their children.
"The dose of thimerasol is very small and would be much less than a child would ingest if they ate a couple of tuna sandwiches a month," she says.
She points out that this study has found only the mechanism by which mercury could enter the brain, but does not confirm whether it is actually happening to children and causing ill effects.
"Parents should realize that there have been five studies looking at the link between thimerosal and autism and none of these studies have found any sort of link," Favaro points out.
"Parents should really not be that concerned."
Deth says he doesn't want to parents to misunderstand how important vaccine programs are to children's health.
"It's not the vaccines that are the problem -- it's the additives," he says.
The study appears in this week's issue of the journal Molecular Psychiatry and was published two months ahead of schedule.