Children with autism spectrum disorder had no greater immune response to the measles virus or the measles component of the measles, mumps, and rubella vaccine than did children without the disorder in a large case-control study
Writing in the Archives of Disease of Childhood, British researchers said that their community sample study of 250 children aged 10–12 years is the largest to date to fail to demonstrate any association between MMR vaccination and autism spectrum disorder (ASD) “using well-validated techniques.”
Concern about the possible connection has led to lower MMR vaccination rates, from 92% in 1995–1996 to 80% in 2004, according to UK Health Protection Agency data cited by the researchers (Arch. Dis. Child. 2007 Feb. 5 [Epub doi:10.1136/adc.2007.122937]).
Led by Dr. Gillian Baird of Guy's and St. Thomas' National Health Service Trust in London, the researchers said uptake of the second MMR vaccination was lower in the children who had autism or autism spectrum disorder than in the control population without autism (29% vs. 50%).
Children with special education needs but not autism spectrum disorder had lower vaccination rates than normal developing children.
These differences in uptake between groups “may reflect parental concern about vaccination following a diagnosis of developmental abnormality,” the researchers wrote.
Four of the authors listed conflicts of interests relating to lawsuits against manufacturers of the MMR vaccines, including Dr. Baird, who has served as an expert witness.
The researchers drew their subjects from a cohort of 56,946 children born between July 1, 1990, and Dec. 31, 1991, from the South Thames region of England.
After screening for autism spectrum disorders and special educational needs, the researchers identified 98 cases of autism spectrum disorders. The cases were compared to 52 control children who had special educational needs but no diagnosis of autism, along with 90 control children with typical development.
The researchers analyzed blood from the subjects to determine whether they had persistent measles infections or abnormally high measles antibodies.
They found no differences in the distribution of measles antibodies or virus in the children with autism spectrum disorder or the controls, regardless of whether children had received one or both of the MMR vaccinations.
There also was no sign of altered persisting immunological response in autism spectrum disorder cases, in those with or without a history of regression.
Regression of language was defined as a loss of at least five words used communicately during a 3-month period, or, in those who had not achieved the five-word stage, “a reported regression of words or skills in social communicative or play behavior.”
Authors of a case series published in 2000 had described a condition referred to as “autism enterocolitis,” postulated to be associated with the MMR vaccine and regression in autism.
Researchers in the current study found no evidence of increased enterocolitis in the autism spectrum disorder group with regression.
Only one child in the study had “possible enterocolitis,” and this child was from a control group
The researchers said their study is strong because of its size, the geographic definition of its sample, good vaccination histories, and a diagnostic procedure that allowed researchers to identify a dose-response relationship between autism symptoms and antibody levels.
However, Dr. Baird and his fellow investigators noted that the control population was not randomly selected, and might therefore have been biased.
The children's parents were informed it was a study about MMR vaccination.