Last week, the U.S. Court of Federal Claims began hearing arguments about whether a childhood vaccine that protects against measles, mumps and rubella caused autism in a 12-year-old (Cedillo versus Secretary of Health and Human Services). Here is a look at the studies behind the controversy.
In 1998, a gastroenterologist named Dr. Andrew Wakefield, then at the Royal Free Medical School in London, examined 12 children with bowel problems. Nine had autism, a disorder that affects 1 in 150 youngsters. The parents of eight recalled that the symptoms started soon after the children received a vaccine against measles, mumps and rubella (the MMR vaccine). Wakefield postulated in an article in the Lancet that the vaccine might cause autism.
"Then he held a press conference and went a bit further," says Rachel Casiday of Durham University in the United Kingdom, who studies peoples' attitudes toward MMR and autism. Wakefield recommended the United Kingdom's Department of Health provide the three vaccines separately. The department refused, due to scientific, logistical and economic reasons. Casiday said this response probably made people think the government wasn't taking the issue seriously, and some parents of autistic children began to wonder.
Autism researcher David Mandell, of the University of Pennsylvania School of Medicine in Philadelphia, says the U.S. government made similar mistakes, with discussions about the potential link being held behind closed doors at the Centers for Disease Control and Prevention in Atlanta. "That gave off the appearance of impropriety," he says.
In 2004, 10 of 12 coauthors of Wakefield's paper retracted the claims in it.
Because of the public's concern, various governments investigated the possible autism-vaccine link with more rigorously-designed studies. Researchers focused on two vaccine components: thimerosal, a mercury-based preservative, and the killed virus that provides the immunization against measles.
Scientists started with studies that looked at how many children were being vaccinated and how many new cases of autism were diagnosed, to see if there was a link between the two, says epidemiologist Craig Newschaffer of Drexel University School of Public Health in Philadelphia. A 2001 study in California, for example, found that between 1980 and 1994, the number of MMR vaccines administered every year rose about 14%, but the autism rates rose 373%. Thus, vaccine administration could not account for the rise in cases of autism.
