In evidence-based scientific circles the MMR vaccine-autism hoax is already firmly nailed shut in a coffin and buried beneath a heavy load of epidemiological studies, virological studies, and revelations about how badly the original work was performed. Even the media seem to have latched on. However, small groups of grave diggers continue to visit it at night, disturbing the earth and performing bizarre acts of ritual quackery above the decayed corpse of a theory. Now, the final invocation they use to revive this revenant appears to be broken.
After the virological studies of Afzal, D’Souza, and Baird, one of the criticisms made was that the studies had not examined the same thing that Wakefield had examined. Therefore, some argued Wakefield’s hypothesis that MMR vaccine was a causal agent for autism could not be discounted.
Wakefield thought he had linked intestinal abnormalities with autism, and parental views on a temporal relationship with MMR vaccination. This led to his first iteration of the MMR vaccine-autism hypothesis. Measles virus RNA was found in bowel tissue and peripheral blood mononuclear cells, although we now know that these results were dubious at best. Wakefield was even told that many of the results in one study were false positives. This was used as proof that MMR vaccine has contributed to autism by some gut associated pathology.
The Afzal, D’Souza, and Baird studies all looked for measles virus RNA in blood, rather than in bowel tissue. As Wakefield said of the Baird study:
it is a major error to have presumed that peripheral blood mononuclear cells are a valid proxy for gut mucosal lymphoid tissues when searching for persistent viral genetic material.
Now Wakefield’s work has been replicated by Hornig et al (Hornig M, Briese T, Buie T, Bauman ML, Lauwers G, et al. (2008) Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study. PLoS ONE 3(9): e3140. doi:10.1371/journal.pone.0003140). This study looked at two groups of children. One group with autism and gut disturbances, and another group with gut disturbances but no neurological problems. They obtained gut biopsies from the children, and had them examined for measles virus RNA in three independent and blinded laboratories. This means the labs did not know which samples came from children with autism or children without autism – thus removing researcher bias. Importantly, the laboratories all correctly identified test samples of positive controls (which should test positive for RNA) and negative controls (which should test negative for RNA).
There was no difference between the autistic and non-autistic children in terms of measles virus RNA in the bowel. One out of the 25 autistic children had measles virus RNA present in the gut biopsies, and 1 out of the 13 children without autism had measles virus RNA present. There was no difference between the groups – which provides evidence that persistent measles virus RNA in the gut (from MMR vaccination) is unlikely to cause autism. In addition, examination of the temporal relationship between MMR vaccination and gut problems did not support Wakefield’s hypothesis.
As the authors put it:
The work reported here eliminates the remaining support for the hypothesis that ASD with GI complaints is related to MMR exposure. We found no relationship between the timing of MMR and the onset of either GI [gut] complaints or autism. We also could not confirm previous work linking the presence of MV [measles virus] RNA in GI tract to ASD [autism] with GI complaints.