A Centers for Disease Control and Prevention (CDC) study released today claims there is no link between the MMR vaccine and autism. The National Autism Association (NAA) says this study does nothing to dispel the growing public concern over a vaccine-autism connection and raises several questions concerning design and methodology.
For years, parents have claimed that MMR triggered their child's subsequent GI (gastrointestinal) disease and autism. In a 2002 paper where the majority of autistic children were found to have measles in their intestines, the children examined showed a clear temporal link between MMR exposure and regression. The CDC's attempt to replicate the 2002 study fell far short of proving the safety of the MMR vaccine.
1. The CDC study was designed to detect persistent measles virus in autistic children with GI problems. The assumption being if there is no measles virus at the long delayed time of biopsy, there is no link between autism and MMR. But NAA says this underlying assumption is wrong. The questions should have been: Do normally developing children meeting all milestones have an MMR shot, develop GI problems and then regress into autism? Do they have evidence of measles and disease in their colons compared to non-vaccinated age and sex matched controls?
2. In the current CDC study, only a small subgroup of children was the correct phenotype to study. From page 7, "Only 5 of 25 subjects (20%) had received MMR before the onset of GI complaints and had also had onset of GI episodes before the onset of AUT (P=0.03)." The other 20 autistic children in the study had GI problems but the pathology developed before the MMR vaccine. Additionally, the controls all received the MMR vaccine and had gastrointestinal symptoms. The controls should have been free of exposure to vaccine measles in order to make a comparison relevant for purposes of causation.