Pervasive developmental disorders (PDD) like autism and Asperger Syndrome have been on the rise for years. Measles Mumps Rubella (MMR) vaccines and thimerosal-containing vaccines (which are approximately 50 percent ethylmercury) have been suggested as possible causes. A new MUHC study, published in the scientific journal Pediatrics today, assesses the link between childhood immunizations and PDD in 28,000 Quebec children and finally clears MMR vaccines and thimerosal-containing immunizations as risk factors.
"There is no relationship between the level of exposure to MMR vaccines and thimerosal-containing vaccines and rates of autism," says Dr. Eric Fombonne, Director of Pediatric Psychiatry at the Montreal Children's Hospital of the MUHC and lead investigator of the new study. Thimerosal was used to prevent bacterial and fungal contamination in the manufacture of various vaccines until its elimination from vaccine formulas in 1996 in Quebec. "According to our data, the incidence of autism was higher in children who were vaccinated after thimerosal was eliminated from vaccines," says Dr. Fombonne.
"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," says Dr. Fombonne. "This action resulted in resurgence of the measles, which caused the deaths of several young children in Europe." Dr. Fombonne's study indicates that autism rates continued to increase even with reductions in the use of MMR vaccinations. "We hope this study will finally put to rest the pervasive belief linking vaccines with developmental diseases like autism," says Dr. Fombonne.
Autism is a neuropsychiatry disorder that impairs a child's ability to communicate and interact with others. The prevalence is about 65 cases per 10,000 people (about 1 child in 155), making autism one of the most common childhood disorders. The Psychiatry Department at the Montreal Children's Hospital sees about 350 new cases of autism each year. However, Dr. Fombonne stresses that there is no demonstrated autism epidemic. He attributes the rise in autism rates to a broader definition of autism and greater awareness of the disorder.
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