The putative association between MMR and autism was first reported in 1998 in a small case series published in Lancet. The report included 12 children, all of whom had inflammatory bowel disease and eight of whom had autism. This study had significant flaws, most notably that case reports do not offer strong proof of causal association. Furthermore, history of MMR receipt was based on parental recall. Because these parents believed that MMR was responsible for their children’s autism, it is not surprising that they reported a temporal association between MMR vaccination and the development of autistic symptoms. There are also ethical concerns about this study based on its funding and the fact that patients were not randomly enrolled. Because of these ethical concerns, Lancet retracted the article in 2010.
Before retraction, the study received substantial media attention, and rates of MMR vaccination significantly decreased in the United Kingdom, where the study was published, and to a much lesser extent in the United States. The MMR-autism hypothesis has never been confirmed. Many large epidemiologic studies that included hundreds of thousands of children have failed to identify an association between MMR and autism. In 2001, the IOM concluded there was no association between MMR and autism and reaffirmed this in 2004 and 2011.