SafeMinds Statement on Measles Virus and Autism Study
scientific study released today examined the hypothesis that measles virus
persisting in the intestinal tract from the MMR vaccine causes or exacerbates
autism. The study refuted this hypothesis for the majority of autism cases while
validating the link between gastrointestinal (GI) disease, inflammation and
autistic regression. The study design precluded assessment of a role for acute
measles infection from MMR in a subset of children with autism and did not
examine the role of other vaccines, vaccine components such as thimerosal, or
other environmental exposures which can trigger gastrointestinal and
immunological problems. The topic is of public health interest due to the
increasing autism epidemic and parent and scientific reports connecting mercury
and vaccines, including MMR, with autism onset.
The study, "Lack of an association between measles virus vaccine and autism with enteropathy: a case-control study" by Mady Hornig and colleagues, appears in this month's PloS One journal. Colon biopsies from 38 children presenting with gastrointestinal disorder, 25 with autism and 13 without neurological differences, were examined for presence of measles virus RNA by three laboratories to ensure validity. All children had been given the MMR vaccine when younger, and except for one subject, the vaccine was given more than 6 months prior to the biopsy, in order to determine persistence. The MMR is a live virus vaccine and failure to clear the attenuated measles virus is a known but rare occurrence after vaccination.
The persistent measles and autism hypothesis, linking bowel disease, autistic regression and MMR, was originally made by Andrew Wakefield and colleagues in 1998. One of the three labs involved in the Hornig study was led by John O'Leary who conducted the testing for the Wakefield study. The three Hornig study labs validated each other, confirming the rigorousness of Dr. O'Leary's work. Dr. O'Leary conducted the testing for one of the autism test cases now in the Federal Court for Vaccine Claims. The child, who regressed into autism and bowel disease after receiving the MMR, tested positive for measles virus. The Hornig study also substantiates the link between autistic regression and gastrointestinal disorder.
The Hornig study found only one autism patient with persistent measles virus. None was detected in the remaining 24 children. This finding differs from the Wakefield and more recent studies which reported a high percentage of children with regressive autism and bowel disease with detectable measles virus. The discrepancy was not explained but may be due to how and when the biopsies were taken or differences in the study samples.
The Hornig findings suggest that persistence may not be a factor but inadequately address whether measles vaccination may lead to an acute reaction that contributes to dysfunction. An acute or 'hit and run' mechanism means that the initial effect occurs and the virus is rapidly cleared. The effect would not require persistence and is how many biological disturbances arise from pathogens and toxins. The study sample was small, making characterization of subgroups difficult. Autism is considered a complex and heterogeneous disorder with multiple, interacting causal and exacerbating factors. The MMR vaccine may have led to dysfunction in a subset of children and other triggers may underlie other cases. While half the autism cases in the study had gastrointestinal or autism symptoms prior to receipt of the MMR, additional triggers such as other vaccines or environmental pollutants acting on the majority of cases would effectively wash out a positive MMR-autism association in a subset.
Larger studies are needed to tease out the role of the various contributors to autism onset and severity of symptoms, including GI problems. These studies need to examine multiple factors, not just one. In particular, a comparison of health outcomes in vaccinated and unvaccinated populations is warranted. The Hornig study has advanced our understanding of gastrointestinal inflammation and autism and casts doubt on measles persistence in most children with autism, but it does not rule out an acute MMR effect in a subset and does not absolve multiple vaccinations or mercury from playing a role in autism.
Click here to read National Autism Association statement on study.