A decade ago, a paper by Andrew Wakefield and colleagues was published in The Lancet, detailing the cases of 12 children with autism spectrum disorder (ASD). Anecdotal reports from parents of several of these children suggested that the onset of their condition followed receipt of the measles, mumps, and rubella (MMR) vaccine. Wakefield concluded following this research that the MMR vaccine was unsafe, and could play a causative role in the development of autism as well as gastrointestinal disease–the first volley in the latest incarnation of anti-vaccination fear-mongering that’s as old as vaccination itself. Well, to the surprise of few, a study has been published in today’s PLoS One showing yet again no link between vaccination and autism–and, as in the original Wakefield study, the authors here looked at the presence of measles virus RNA in intestinal tissue. More after the jump.
Originally, Wakefield had suggested that because MMR contains live virus (particularly live measles virus), an inappropriate immune response to the viruses in the vaccine may cause other pathologies, including autism spectrum disorders and bowel disease. The 1998 Lancet paper laid out this link:
We have identified a chronic enterocolitis in children that may be related to neuropsychiatric dysfunction. In most cases, onset of symptoms was after measles, mumps, and rubella immunisation.
Like the original study, this one was fairly small (though notably, still about 4 times as large as Wakefield’s). 47 kids were recruited, and 38 were included in the final analysis. They also used a case-control study design, rather than the original case series (in which the selection of kids was a huge conflict of interest, as Wakefield was actually paid by many of the childrens’ parents to find evidence of a vaccine-autism link).
They then examined the cases and controls using a molecular assay to detect measles virus RNA. Because other investigators couldn’t repeat Wakefield’s finding of measles virus RNA in kids with ASD, this study repeated all the assays in 3 independent labs, which were blinded as to the status of the samples.
So, what did they find? Obviously, no association. In addition:
We found the age at the time of exposure to MMR relative to onset of GI problems in cases and controls and the temporal order of MMR administration, GI episodes, and AUT onset in cases to be inconsistent with a causal role for MMR vaccine as a trigger or exacerbator of either GI disturbances or autism.
It should be noted that there are several of limitations with the study. Most notably, the size was still small, but it’s difficult to do a large study like this because of the rather invasive nature of the sampling (bowel biopsy). However, the investigator blinding and replication of results in three separate laboratories help to offset the size issue.
Do I expect these negative results to make a damn bit of difference with the Jenny McCarthy crowd?
Mady Hornig, Thomas Briese, Timothy Buie, Margaret L. Bauman, Gregory Lauwers, Ulrike Siemetzki, Kimberly Hummel, Paul A. Rota, William J. Bellini, John J. O’Leary, Orla Sheils, Errol Alden, Larry Pickering, W. Ian Lipkin, Mark R. Cookson (2008). Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study PLoS ONE, 3 (9) DOI: 10.1371/journal.pone.0003140