Geraldine Dawson, Ph.D., Autism Speaks Chief Science Officer
On Thursday, August 25, the Institute of Medicine’s Committee to Review Adverse Effects of Vaccines Board on Population Health and Public Health Practice released its report on the scientific evidence related to adverse effects of vaccines. The Institute of Medicine (IOM) is a non-profit, non-governmental organization which is part of the National Academy of Sciences. IOM members are scientific and medical experts who serve as pro bono as advisors to the U.S. Congress and other policy-makers. They are periodically asked to provide a review of the evidence on matters of public concern and welfare.
Among several other topics, the IOM committee specifically reviewed the evidence regarding whether the MMR vaccine or the DTaP vaccine is causally linked to autism. In addition to reviewing epidemiological evidence, they reviewed case studies and research on biological mechanisms that might explain a connection between a vaccine and an adverse outcome, such as autism. They specifically assessed the evidence that vaccines could alter neuronal development resulting in autism symptoms, arising from chronic encephalopathy, mitochondrial disorders or other underlying disorders. The committee reviewed 22 epidemiological studies that evaluated the connection between risk for autism and the MMR vaccine and concluded that the evidence does not support a causal link between the MMR vaccine and autism. The committee only found one study on the relationship between the DTaP vaccine and autism and concluded that the data were insufficient to assess an association.
The committee noted that reports of case studies linking the onset of autism to infectious diseases such as encephalitis and malaria suggest that infection or inflammation may underlie some cases of autism. Furthermore, evidence from postmortem brain tissue suggests that autism may involve inflammatory processes affecting the brain. The authors argue that, at a minimum, prior to ascribing autism to vaccination it would be important to rule out chromosomal and single-gene defects, including a variety of metabolic (e.g. mitochondrial disorder) and inflammatory or infectious diseases that may exist prior to vaccination.
The IOM report is consistent with Autism Speaks’ policy statement on vaccines. Given the present state of the science, the proven benefits of vaccinating a child to protect them against serious diseases outweigh the hypothesized risk that vaccinations might cause autism. Autism Speaks continues to support research that explores the relationship between innate or acquired metabolic, inflammatory, or infectious diseases that may play a role in the etiology of autism.