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July 2007
Evidence-Based Tip
Autism & Vaccinations: What does the evidence say?
On June 11, a special U.S. court began hearing arguments from lawyers representing parents of children with autism. These parents are claiming that their children's autism was caused by vaccination and are seeking compensation under the National Vaccine Injury Compensation Program. The news media carried reports of this case, most without referring to the medical evidence showing the safety of MMR and other vaccinations. These stories and the many Internet blogs about autism are fueling parent's fear of vaccination.
One of the contributors to the controversy is a study published in Britain in 1998 by Wakefield et al that did not prove an association between the MMR vaccination and autism. However, the authors suggested that a genetic predisposition to autistic disorders, along with functional vitamin B12 deficiency or chronic enterocolitis that was discovered after vaccination, might be related to the development of developmental regression. Even this weak inference was later retracted by 10 of its 12 authors, and the first author was found to have a conflict of interest.
So, what does the evidence say about the connection between the MMR vaccine and autism? In 2003, a systematic review published in the Archives of Pediatric Adolescent Medicine looked at all studies that examined the connection suggested by Wakefield, and found "no evidence of the emergence of an epidemic of ASD related to the MMR vaccine." The most recent systematic review finds 139 articles and accepts 31 studies as meeting its criteria. It finds "no credible evidence of an involvement of MMR" with autism. No studies done since 2004 provide any evidence linking MMR with autism.
The health implications for unvaccinated children are clear. In Japan, vaccines were withdrawn after two deaths were assumed to be related to a combined DTP and MMR vaccine. The next year, 40 children died from pertussis. As recently as 2002, more than 30,000 cases of measles were reported along with 15 to 90 deaths each year; 650 children became deaf after contracting mumps in 2001; and, local epidemics of rubella occur every year. Recent campaigns to encourage parents to vaccinate their children are helping to reduce disease outbreaks.
Further studies on the etiology of autism may provide better answers for worried parents. For now, studies suggest that the health care provider's ability to listen to parents' concerns and to address their fears with compassion and understanding, along with sharing the evidence, will help these parents make the best decisions for their children's health.
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