For the past few years, scattered studies have delivered ominous warnings that a common vaccine for measles, mumps, and rubella might be behind the increase in the number of children diagnosed with autism. A sweeping new study seems to quash that theory. Kreesten Meldgaard Madsen of the Danish Epidemiology Science Center in Arhus analyzed medical records of more than 500,000 Danish children and found no link between the vaccine and autism.
Symptoms of autism tend to appear around the age of 18 months, about when children receive the inoculation. That synchrony led some parents and researchers to blame the vaccine for the rise in autism. "We went into this study with an open mind, saying that if this is true, it's terrible," says Madsen. When he and his colleagues looked at the data, however, they found vaccinated and unvaccinated children had almost the same risk of developing the disease. "No matter how we twisted the data, we didn't see a correlation," he says.
Diana Schendel, a health scientist at the Centers for Disease Control and Prevention in Atlanta and one of Madsen's coauthors, cites other possible reasons for the autism uptick, from changes in diagnostic criteria to environmental influences. The CDC is establishing programs across the country to monitor the disease and zero in on its causes.