MONDAY, Feb. 4, 2008 (HealthDay News) -- Yet another study has found no evidence of a link between the measles, mumps and rubella (MMR) vaccine and autism.
The British authors of this latest research said theirs was the third and largest study that has looked for a connection between the MMR vaccine and autism, and has failed to find one.
"I think it's fabulous that they have scientifically, God willing, put this issue to rest, although parents will not agree with it and those people who are proponents of measles as the cause [of autism] will find a problem with the paper," said Dr. Pauline A. Filipek, an associate professor of pediatrics and neurology at the University of California, Irvine.
The British researchers based their finding on a sample of 240 children -- 98 who had been diagnosed with autism, and two comparison groups: 52 children with special educational needs who were not autistic; and 90 children who had no developmental problems.
All the children had received the MMR vaccine, but not all had had both doses. The researchers checked blood samples from all the children to look for the presence of persistent measles infection or an abnormal immune response. An abnormal response would have been indicated by circulating measles virus or increased antibody levels.
The researchers found the blood analysis showed no difference in circulating measles virus or antibody levels among the children. The finding was the same whether the children had one or two doses of the MMR vaccine.
In addition, autistic children and those with special educational needs were less likely to have had the second dose of the MMR vaccine, which may mean that parents were concerned about their children receiving the second dose because of their developmental problems.
The findings are reported in the February issue of the Archives of Disease in Childhood.
The controversy about the potential connection between autism and the MMR vaccine began in 1998 when British researcher Dr. Andrew Wakefield published a study in The Lancet that claimed the vaccine caused brain damage, resulting in autism.
Since that time, numerous studies have failed to confirm Wakefield's hypothesis.
"This study refutes the data Wakefield presented 10 years ago," Filipek said.
Filipek thinks parents hold onto the MMR vaccine-autism theory because "it gives them something to grasp onto that could be altered to prevent future cases of autism."
Dr. Paul A. Offit, director of the Vaccine Education Center and chief of infectious diseases at Children's Hospital of Philadelphia, also thinks the new study provides more conclusive evidence that there is no connection between autism and the MMR vaccine.
"The whole premise by Wakefield, that the measles component of [the] MMR vaccine caused a chronic intestinal inflammation that allowed harmful proteins to enter the bloodstream and ultimately the brain, causing autism, has not one shred of scientific evidence in its support," Offit said.
This new study follows the release last week of a study that showed the mercury preservative thimerosal, used in childhood vaccines until the turn of this century and thought by some to be associated with autism, doesn't remain in an infant's body long enough to build to dangerous levels.
And it follows a series of other studies, including a large-scale U.S. Institute of Medicine review in 2004, that failed to uncover a link between childhood vaccines and autism.
Current estimates by the U.S. National Institutes of Health say that one American child in 150 has been diagnosed with autism, although experts wonder if that increase is due in part to better diagnoses and a broader definition of the disorder.
More information
For more on autism, visit the U.S. National Institutes of Health.
