A new study attempting to replicate the original findings from a decade ago linking the measles-mumps-rubella (MMR) vaccine with autism has failed to establish a connection between the two.
In 1998, Dr. Andrew Wakefield, at the time a UK surgeon, published a paper in the medical journal The Lancet that suggested a link between the MMR vaccine and both autism spectrum disorder (ASD) and gastrointestinal (GI) disturbance in children. The study reportedly found measles virus (MV) RNA in the bowel tissue of ASD patients, and sparked public fear that vaccines may contribute to rising rates of autism. Since then, lower rates of vaccination have been reported in some countries, and there has been a resurgence of measles in the US and parts of Europe.
Multiple scientific studies have been published since Wakefield's, and they have found no link between MMR or mercury (or wifi signals for that matter) and autism, but the suspicion that vaccines are responsible is still prevalent. Meanwhile, Wakefield is currently undergoing disciplinary action for professional misconduct, as he took money from lawyers representing autistic children years before gathering data for his study; and 10 of his 11 collaborators have also asked that their names removed from the controversial paper.
The new article, openly available through the Public Library of Science, notes that 20 studies found no temporal relationship between MMR and ASD, and another three found no MV RNA in bowel biopsies of children previously diagnosed with ASD. But according to the study's authors, from Columbia University in New York and the U.S. Centers for Disease Control and Prevention in Atlanta, no published study "from other research groups have addressed whether MV RNA is present in bowel of ASD children with GI disturbances"—the reported results in 1998 of Wakefield's research.
This new research involved 38 children divided into two groups: 25 diagnosed with ASD and GI disturbances, and 13 children with GI disturbances only to act as a control group. All of the children who completed the study had received at least one dose of the MMR vaccine, and had an ileocolonoscopy performed to gather ileal (part of the small intestine) and cecal (where the large and small intestines join) tissues. These tissues were then sent to three labs around the world to check for the presence of MV RNA, including the lab involved in the Wakefield study.
The labs were blind to the group that each sample came from. Two boys who participated in the study did have MV RNA found in their ileal tissue—one was diagnosed with autism, while the other was not. Since MV RNA was not found in any other participants, the authors concluded, "the presence of MV sequences was not associated with an [autism] diagnosis."
The researchers also checked whether a temporal relationship exists between the onset of GI disturbances, ASD, and the administration of the MMR vaccines. For MMR to cause these events, it would have to have been administered before the onset of any symptoms. The authors used the following heuristic: if MMR administration and GI problems began in the same month, it was assumed MMR came first; if GI problems and ASD began in the same month, it was assumed the GI came first; and, finally, if MMR administration and ASD appeared in the the same month, it was assumed that MMR came first. Using this tie-breaker scheme, the data showed no significant correlation in the timing of the MMR vaccine and the onset of GI problems. Nothing suggested that MMR had any role in "either the pathogenesis of [autism] or GI dysfunction."
The authors concluded that this study, which revisited the original MMR-autism plus GI problems link, provided "strong evidence against association of autism with persistent MV RNA in the GI tract or MMR exposure." They did, however, find that children with ASD and GI disorders were associated with higher levels of "regression in language or other skills." The authors suggested this may hint that individuals who suffer from both ASD and GI problems may have a specific type of autism, distinct from other variations.
PLoS One, 2008. DOI: 10.1371/journal.pone.0003140