Vaccines and Autism What do Epidemiological Studies Really Tell Us? VACCINES AND AUTISM – WHAT DO EPIDEMIOLOGICAL STUDIES REALLY TELL US? Coalition for SAFE MINDS

Online at: http://www.ncbi.nlm.nih.gov/pubmed/11581466 Details: A link had been hypothesized between MMR vaccine and a type of ASD where developmental regression and gastrointestinal symptoms appear shortly after vaccination. The hypothesis involves 3 claims: 1) this is a new type of ASD, 2) this new type is responsible for the reported ASD rate increase, and 3) this new type is associated with symptoms suggestive of persistence of measles infection. If such a new "autistic enterocolitis" syndrome had some validity, then 1 or more of the following 6 predictions should be supported by empirical data: 1) Childhood disintegrative disorder has become more frequent 2) The age of first parental concern for ASD children exposed to MMR is closer to the average age of vaccination than in non-exposed children 3) ASD regression autism has become more common in MMR-vaccinated children 4) The age of onset for regressive ASD clusters around the MMR and is different from that of autistic children without regression. 5) Children with regressive autism have distinct symptom and severity profiles 6) Regressive autism is associated with gastrointestinal symptoms and/or inflammatory bowel disorder. The authors used three samples. Data on 96 children (95 immunized with MMR at a median age of 13.5 months) in the UK who were born between 1992 and 1995 and had a PDD diagnosis were compared with data from two other clinical samples (1 pre-MMR [n = 98] and 1 post-MMR [n = 68]) of patients with autism. Reliability was excellent on Autism Diagnostic Interview-Revised (ADI-R) scores, age of parental concern, and developmental regression. Data on bowel symptoms were also available from pediatric and parental sources, while vaccination dates were obtained from computer records. Results: The authors state that prevalence of childhood disintegrative disorder was 0.6per-10 000 – a very low rate, consistent with other estimates, and not suggestive of an increased frequency of this form of pervasive developmental disorder in samples of children who are immunized with MMR. Meanwhile there was no difference in the timing of first parental concern between the two MMR-exposed samples (19.3 and 19.2 months) and the pre-MMR sample (19.5 months). ―Thus‖ the authors claim ―MMR immunization was not associated with a shift toward an earlier age for first parental concerns. Meanwhile, the proportion of children with developmental regression reported in the post-MMR sample (15.6%) was no different from the pre-MMR sample (18.4%); and there was no suggestion that ASD regression had increased in frequency since MMR was introduced. The authors note that children with regressive ASD had no other developmental or clinical characteristics, a finding which, they claim, would have argued for a specific, etiologically distinct phenotype. Parents of regressive ASD children detected the first symptoms at a very similar age (19.8 months) to those of autistic children without regression (19.3 months), and the difference in time between MMR vaccination and parental recognition was not significant (248 vs. 272 days). GI symptoms were reported in 18.8% of cases, with constipation the most common (9.4%). No inflammatory bowel disorder was reported, nor was there any association between regression and GI symptoms. Only 2.1% of the sample had both GI symptoms and regression, ―a rate (sic) that did not exceed chance expectations.‖ Author’s Conclusions: ―No evidence was found to support a distinct syndrome of MMR-induced autism or of ̳autistic enterocolitis‘,‖ and the study adds to ―large-scale epidemiologic studies that all failed to support an association between MMR and autism at the population level.‖