MMR Vaccine and Autism
On November 12, 2000, the CBS television show 60 Minutes featured a story on the MMR vaccine and its alleged link to autism. In 1998, investigators published a report12(pp637-41) on 12 children referred to a London pediatric gastroenterology unit for the evaluation of gastrointestinal diseases associated with developmental regression. The parents of eight of these children associated the onset of behavioral symptoms with the administration of MMR vaccine. The investigators identified lymphoid nodular hyperplasia in 10 children and postulated that “the consequences of an inflamed or dysfunctional intestine may play a part in behavioural changes in some children.”12(p639) However, behavioural symptoms preceded bowel symptoms in four of the six children for whom the onset of bowel symptoms was known. The investigators stated, “We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described.”12(p641)
In 1999, other investigators published the findings of a much larger population-based study conducted in North London.13(pp2026–9) The study identified 498 children with autism but found no temporal association between onset of the disorder and receipt of MMR vaccine in the previous one to two years. Cases of developmental regression were not clustered in the months after vaccination. The investigators concluded, “Our analyses do not support a causal association between MMR vaccine and autism. If such an association occurs, it is so rare that it could not be identified in this large regional sample.”13(p2026)
Another set of investigators found no vaccine-associated cases of inflammatory bowel disease or autism in 1.8 million Finnish children who received almost 3 million doses of MMR vaccine over 14 years.14 In California, retrospective analyses15 of MMR immunization coverage and children with autism also did not suggest an association between MMR vaccine and an increased incidence of autism.
The Institute of Medicine (IOM) recently concluded that “the evidence favors rejection of a causal relationship at the population level between MMR vaccine and ASD (autistic spectrum disorders).”16(p9) However, the IOM could “not exclude the possibility that MMR vaccine could contribute to ASD in a small number of children.”16(p9)
Data on measles, mumps, and rubella disease and MMR vaccine11,14,17–23 are summarized in Table 1.24