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Unformatted text preview: Abstract It has been suggested that the measles, mumps, and rubella vaccine (MMR) is a cause of regressive autism. As MMR was used in Japan only between 1989 and 1993, this time period affords a natural experiment to examine this hypothesis. Data on 904 patients with autism spectrum disorders (ASD) were analyzed. During the period of MMR usage no significant difference was found in the incidence of regression between MMR-vaccinated children and non-vaccinated children. Among the proportion and incidence of regression across the three MMR-pro- gram-related periods (before, during and after MMR usage), no significant difference was found between those who had received MMR and those who had not. Moreover, the incidence of regression did not change significantly across the three periods. Keywords MMR Autism ASD Regression Introduction The measles, mumps, and rubella (MMR) vaccine has been suggested as a possible cause of a new variant of regressive autism (Wakefield et al., 1998 ). In Japan, the MMR vaccination was introduced in April 1989, when the Japanese government recommended that the MMR vaccine or a monovalent measles vaccination be given once to toddlers between the age of 12 and 36 months. In Japan, only one shot of MMR was included in the immunization schedule. The monova- lent mumps and rubella vaccine remained the optimal choice of vaccine for those who did not participate in the MMR program. In Japan, the MMR vaccine con- tained AIK-C (measles), Urabe AM9 (mumps), and To-336 (rubella) strains. However, soon after the introduction of the MMR program, there were several cases of aseptic meningitis, which may have been caused by the Urabe strain of the mumps virus (Sugi- ura & Yamada, 1991 ). As a result, in April 1993, the Japanese government ceased extensive inoculation with MMR (Takahashi, Arai, Tanaka-Taya, & Okabe, 2001 ; Takahashi et al., 2003 ). Wakefield et al. ( 1998 ) have postulated that the MMR vaccination causes a variant of autism associated with developmental regression and bowel symptoms. This hypothesis predicts that the incidence of regres- sive autism should be higher in children given the MMR vaccine, and that, in the case of Japan, the incidence of regression in autism should have increased following the introduction of the MMR program and decreased after it ceased (Taylor et al., 2002 ). In order to investigate whether the MMR vaccination is asso- ciated with regressive autism, we examined the rate of autism spectrum disorders (ASD) 1 involving T. Uchiyama ( & ) Department of Human Welfare, Otsuma Womens University, 2-7-1, Karakida, Tama-city, Tokyo 206-8540, Japan e-mail: email@example.com T. Uchiyama Yokohama Psycho-developmental clinic, Yokohama, Japan M. Kurosawa Y. Inaba Department of Epidemiology and Environmental Health, Juntendo University School of Medicine, Tokyo, Japan 1 The definition we followed was that of pervasive developmental disorders in DSM-IV, but, following most current practice we...
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