Study identifies association between pattern of MMR exposure and regressive autism

"Is There a 'Regressive Phenotype' of Autism Spectrum Disorder Associated with the Measles-Mumps-Rubella Vaccine? A CPEA Study"; Richler J et al. Journal of Autism and Developmental Disorders. 2006; April 28.

A recent multi-center Collaborative Programs of Excellence in Autism (CPEA) study examined:

(i) whether there is a regressive phenotype of autism;
(ii) whether this phenotype is associated with gastrointestinal symptoms; and,
(iii) whether this phenotype is associated with exposure to the MMR vaccine.

One of the more compelling observations to emerge from this study was a clear association between significant gastrointestinal symptoms and regressive autism, compared with children who exhibited features of autism from an early age. Of particular interest is the observation of an association between children with the 'regressive phenotype', age of onset of regression, and age of MMR vaccination.

The authors defined the children of interest - the 'regressive' phenotype - as those with normal or near normal skills before MMR vaccination who regressed after MMR vaccination and who had had at least one gastrointestinal symptom for three consecutive months at some point in his or her life. When these children were compared with the remaining autistic group, there was a statistically significant difference in the sex ratio (more females in the phenotype group); significantly later age of onset in the phenotype group (a mean of 19 months compared with 14.55 months) and lower age at MMR vaccination (14.38 months versus 17.71 months).

The later observation is particularly interesting in view of the fact that age of exposure to measles virus is a major determinant of the risk of an adverse outcome. Children exposed to measles early in life are at greater risk of persistent (long-term) infection and delayed neurologic disease. This risk diminishes as children get older. Persistent infection with measles virus in children with regressive autism has been reported by Thoughtful House scientists and replicated in a study that is due to be presented at the International Meeting for Autism Research (IMFAR) in Montreal June 1-3. The observation in the current paper that younger age at MMR vaccination is associated with regressive autism in children with intestinal symptoms is therefore entirely consistent with an adverse outcome from MMR vaccine.

It is most surprising that, in view of their findings, the authors conclude in the paper’s abstract that "there was no evidence that onset of autistic symptoms or of regression was related to measles-mumps-rubella vaccination." Further clarification of this apparently irreconcilable contradiction is being sought from the authors of the study.

AJW & CS

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