California Study Finds No Conclusive Link Between Autism and MMR

California researchers dispute the possible connection between autism and the MMR vaccine in a study in today's Journal of the American Medical Association. Researchers from the California Department of Health Services Immunization Branch compared the MMR immunization information of children born between 1980-1994, diagnosed with autism and enrolled in the California Department of Developmental Services (an agency that coordinates care and support for children with autism) to children of the same age who were enrolled in California kindergartens. Researchers observed no correlation between the trend of early childhood MMR immunization rates and the trend of children with autism who were enrolled in the state program. Between 1980 and 1994, researchers noted an increase in the number of autism cases reported, from 44 cases per 100,000 live births in 1980 to 208 cases per 100,000 live births in 1994 (an increase of 373%). However, during the same time period, the percentage of children receiving immunization by the age of 24 months increased from only 72% to 82% (an increase of 14%).

From these results, the researchers conclude, "The lack of correspondence between the trends in MMR coverage and numbers of autistic disorder cases does not support the hypothesis that increasingly widespread MMR immunization of young children is associated with the marked secular trend of increasing numbers of autism cases" (Dales et al. JAMA, 3/7 issue). Dr. Study author Loring Dales said, "We have good data and we looked carefully for any evidence that MMR could have caused this increase (in autism)." Two other recent studies -- one published in the Feb. 17
British Medical Journal and a Finnish study -- back up the California study, the Los Angeles Times reports.

Discussion about a "purported link" between the MMR vaccine and autism began when parents observed their children were "apparently developing normally until they received the vaccine," the Times reports. Furthermore, a 1998 report by Dr. Andrew Wakefield of the London-based Royal Free Hospital said that 12 children who had experienced regression within 14 days of receiving the MMR vaccine had gastrointestinal problems; in addition, the weakened virus used in the measles vaccine was contained in their intestines. Wakefield said that the virus might have allowed "potentially toxic" components of food to travel through the blood to the brain, where they damaged neurons and produced developmental problems. Wakefield plans to release a larger study on the issue.

Parents and advocates who believe the vaccine is linked to autism disputed the California study's results. Rick Rollens, a parent advocate, said, "I don't know why anyone would believe information that comes out of a branch whose sole purpose is to promote immunization in California." He added that the British and Finnish studies are "equally questionable" because vaccine makers sponsored them. Dr. Bernard Rimland of the San Diego-based Autism Research Institute said, "It's much to early to dismiss the (vaccine) hypothesis," arguing that the MMR vaccine alone does not trigger autism, but together, the 22 separate vaccines that children receive between birth and age two places a "burden" on the immune system. In 1980, children received eight vaccines by the age of two, but now receive 22. Rimland said, "There is good reason to believe that the immune system is not up to this kind of mistreatment" (Maugh, Los Angeles Times, 3/7).