No link between MMR vaccination and autism - Study by international team to be published in the Lancet

Under embargo until
6:30 p.m. e.s.t. September 9, 2004
as per restriction imposed by The Lancet

Parents worried by the media coverage of a possible link between MMR (measles, mumps, rubella) vaccination and autism can relax. A major new study has concluded MMR vaccination is not associated with increased risk of autism. The study, co-authored by Dr. Eric Fombonne, Director of the Department of Psychiatry at the Montreal Children's Hospital of the McGill University Health Centre (MUHC) will be published in the September 11 edition of The Lancet, one of the world's leading medical journals.

Worries over a possible link between MMR vaccination and pervasive developmental disorders (PDDs) such as autism have led to a decrease in the number of children receiving the vaccination. PDDs are a range of disorders including autism and Asperger's syndrome. Symptoms include abnormalities in language development, communications and social skills, and repetitive behaviours.

The MMR vaccine protects children against measles, mumps and rubella (German measles), three potentially serious childhood diseases which can cause long-term complications or even death. The decline in vaccination coverage has resulted in measles outbreaks in the last several years.

"In light of the continuing concern about a link between MMR vaccination and autism, we decided to undertake a large case-control study to gain a very clear understanding of possible risk," says Dr. Fombonne. "We used over 5,000 computerized records from general practice to see whether children who received MMR vaccinations had a higher risk of developing autism or another PDD than children who did not receive the vaccine. We found that MMR vaccination was not associated with increased risk of autism or other PDDs."

To further test their hypothesis, researchers combined their results with those of three previous studies comparing risk of PDD in vaccinated and unvaccinated children. Results from all four studies were similar. The combined results of these studies provide the most compelling confirmation to date that MRR vaccination is not associated with increased risk of PDDs.

"There is no convincing evidence that MMR vaccinations increase the risk of autism or other PDDs," says Dr. Fombonne. "No significant association has been found in rigorous studies in a range of different settings.

"Autism and other PDDs are severe diseases, and very little is known about what causes them," he adds. "The very absence of knowledge in this area may have contributed to the mistaken idea that MMR vaccination was linked to PDDs. Without question, research into the real causes of autism and other PDDs is urgently needed."