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A new study by researchers at the Mailman School of Public Health helps dispel a persistent belief that the vaccine for measles is linked to autism.

"We found no connection between autism and the measles, mumps and rubella (MMR) vaccine," said W. Ian Lipkin, senior author of the study and director of the Mailman School's Center for Infection and Immunity. Lipkin is also the John Snow Professor of Epidemiology and professor of neurology and of pathology.

The results come amid an alarming rise in measles cases, as some parents have forgone the measles vaccine for their children in part because of fears of an autism link. From Jan. 1 through July 2008, the Centers for Disease Control and Prevention (CDC) received 131 reports of confirmed measles virus infections in the United States, the highest number for the same time period since 1996. Of these cases, 91 percent occurred in individuals who had not been vaccinated or had unknown vaccination status.

Measles is a serious, highly contagious disease, which spreads when people touch or breathe in infectious droplets passed by coughing and sneezing. It is the most deadly of all childhood rash/fever illnesses, according to the CDC. Before the measles vaccine was introduced in 1963, three to four million people contracted measles each year— 400 to 500 died, 48,000 were hospitalized and 1,000 developed chronic disability. The MMR vaccine, a combined vaccine for measles, mumps and rubella viruses, is the safest protection against measles, the CDC says.

In 1998, a small study of children with autism raised the question of a link between the neuropsychiatric condition and the MMR vaccine. The researchers suggested that vaccination with MMR caused gastrointestinal (GI) problems in the children, which then led to autism. (Most of the researchers, however, later retracted the study's interpretations, stating that the data weren't sufficient to establish this link.) Additional studies in 2002 found evidence of measles virus in the intestinal tissues from 77 percent of children with autism and GI inflammation, but in none of the intestinal biopsy tissues from normal control children.

Since then, other larger epidemiologic studies have found no associations between the MMR vaccine and autism, but no subsequent research had tested for the presence of measles virus in intestinal tissues of children with autism and GI problems, nor did they examine the temporal relationship of MMR, GI problems and autism. The absence of such research may have contributed to persistent concerns over the vaccine, influencing parents' decisions to vaccinate or not, and contributing to the increased outbreaks of measles.

In Mailman's case-control study, scientists at the school's Center for Infection and Immunity and researchers at Massachusetts General Hospital, Trinity College Dublin and the CDC evaluated bowel tissues from 25 children with GI disturbances and autism and 13 children with GI disturbances but without neurodevelopmental problems for the presence of measles virus RNA. In the study, the presence of measles virus was no more likely in children with autism and GI disturbances, than in children with only GI disturbances. Evidence of measles virus was found in only one case and one control, at levels just above the threshold for detection.

"We [also] found no relationship between the timing of MMR vaccine and the onset of either GI complaints or autism," said Mady Hornig, associate professor of epidemiology, director of translational research in Mailman's Center for Infection and Immunity and lead author of the study. "Our results are inconsistent with a causal role for MMR vaccine as a trigger or exacerbator of either GI difficulties or autism."

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