Saturday, July 08, 2006

Canadian study casts doubt to link to vaccines and Autism Spectrum Disorder

A new Canadian study is casting doubt on the theory that mercury-based vaccines and childhood immunizations lead to an increased risk of autism.
"There is no relationship between the level of exposure to MMR vaccines and thimerosal-containing vaccines and rates of autism," said Dr. Eric Fombonne, lead investigator of the new study, which will be published Wednesday in the journal Pediatrics.
The MMR vaccine is a three-in-one needle that protects against measles, mumps and rubella.
The findings suggest that autism rates continued to increase even after reductions in MMR jabs and the elimination of thimerosal, a controversial mercury-based vaccine preservative.
"According to our data, the incidence of autism was higher in children who were vaccinated after thimerosal was eliminated from vaccines," said Fombonne, director of pediatric psychiatry at The Montreal Children's Hospital of the McGill University Health Centre (MUHC).
Thimerosal was used to prevent bacterial and fungal contamination in the manufacture of various vaccines until it was phased out of such formulas in 1996 in Quebec.
Currently in Canada, some influenza and hepatitis B vaccines are the only thimerosal-containing products that might be offered to children as part of the routine immunization schedule.
While high doses of mercury can cause neurological damage, there has been no evidence that this type of damage causes the symptoms specific to autism.
"In the past, concern about a potential link between MMR vaccinations and autism led some parents to take the drastic step of refusing to inoculate their children against dangerous childhood diseases like measles," said Fombonne.
"This action resulted in resurgence of the measles, which caused the deaths of several young children in Europe."
Concerns were raised in the late 1990s when a leading medical journal published a study that claimed a link between childhood vaccinations and autism.
Though the 1998 research published in the Lancet has since been discredited, medical officials have noted a drop in immunization rates.
Fombonne's study found:
After thimerosal was eliminated, the autism rate rose from 59.5 per 10,000 to 82.7 per 10,000.
The findings also reveal that after MMR immunizations declined in the late 1990s, the rate climbed to 102.5 per 10,000 compared to 40.6 in the late 1980s.
"And that is consistent with many studies which have been done in the UK and in the U.S. showing a relationship between MMR and autism," Fombonne told CTV Montreal.
But Mario Provost, a Montreal parent of a seven-year-old severely autistic child, said no study will convince him that his son's autism was not caused by a vaccine.
Provost said when his son Sean received the MMR vaccine at 20 months, he appeared to be in perfect health. But within 48 hours, Provost said his son began to change.
"After (he took) the vaccine, no more," Provost told CTV Montreal. "(There was) no more speaking out, nothing. We lost the kid completely."
He is convinced the mercury used as a preservative in the vaccine is to blame.
But numerous studies conducted since the British one that raised alarm bells a decade ago have found no such link.
Common disorder
Autism is a common neuropsychiatry disorder that impairs a child's ability to communicate and interact with others.
About one child in 155 is diagnosed as autistic, the study says, making autism one of the most common childhood disorders.
The Montreal Children's Hospital sees about 350 new cases of autism each year. However, Fombonne stresses that there is no autism "epidemic."
He attributes the rise in autism rates to a broader definition of autism and greater awareness of the disorder.
The MUHC study examined the link between childhood immunizations and the development disorder in 28,000 Quebec children between 1987 and 1995.
With a report from CTV Montreal's Caroline van Vlaardingen