A Population-Based Study of Measles, Mumps, and Rubella Vaccination and Autism

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New England Journal of Medicine Nov. 7, 2002A Population-Based Study of Measles, Mumps, and Rubella Vaccination andAutismKreesten Meldgaard Madsen, M.D., Anders Hviid, M.Sc., Mogens Vestergaard,M.D., Schendel, Ph.D., Jan Wohlfahrt, M.Sc., Poul Thorsen, M.D., JørnOlsen, M.D., and Mads Melbye, M.D.ABSTRACTBackground It has been suggested that vaccination against measles, mumps,and rubella (MMR) is a cause of autism.Methods We conducted a retrospective cohort study of all children born inDenmark from January 1991 through December 1998. The cohort was selected onthe basis of data from the Danish Civil Registration System, which assigns aunique identification number to every live-born infant and new resident inDenmark. MMR-vaccination status was obtained from the Danish National Boardof Health. Information on the children's autism status was obtained from theDanish Psychiatric Central Register, which contains information on alldiagnoses received by patients in psychiatric hospitals and outpatientclinics in Denmark. We obtained information on potential confounders fromthe Danish Medical Birth Registry, the National Hospital Registry, andStatistics Denmark.Results Of the 537,303 children in the cohort (representing 2,129,864person-years), 440,655 (82.0 percent) had received the MMR vaccine. Weidentified 316 children with a diagnosis of autistic disorder and 422 with adiagnosis of other autistic-spectrum disorders. After adjustment forpotential confounders, the relative risk of autistic disorder in the groupof vaccinated children, as compared with the unvaccinated group, was 0.92(95 percent confidence interval, 0.68 to 1.24), and the relative risk ofanother autistic-spectrum disorder was 0.83 (95 percent confidence interval,0.65 to 1.07). There was no association between the age at the time ofvaccination, the time since vaccination, or the date of vaccination and thedevelopment of autistic disorder.Conclusions This study provides strong evidence against the hypothesis thatMMR vaccination causes autism.Source Information>From the Danish Epidemiology Science Center, Department of Epidemiology andSocial Medicine, Århus, Denmark (K.M.M., M.V., P.T., J.O.); the DanishEpidemiology Science Center, Department of Epidemiology Research, StatensSerum Institute, Copenhagen, Denmark (A.H., J.W., M.M.); and the NationalCenter on Birth Defects and Developmental Disabilities, Centers for DiseaseControl and Prevention, Atlanta (D.S.).Address reprint requests to Dr. Madsen at the Danish Epidemiology ScienceCenter, Department of Epidemiology and Social Medicine, Vennelyst Blvd. 6,DK-8000, Aarhus C, Denmark, or at kmm@....