After a decade of controversy that has seen surges in measles outbreaks because of many parents’ mistrust of the vaccine, a new US-led study concluded there is no link between the MMR vaccine and the onset of autism or gastrointestinal symptoms in children who develop both. The new study replicated the 1998 UK study that originally suggested there was a link between MMR and autism because it found measles virus in the bowels of a group of autistic children with gastrointestinal disorders who had been vaccinated.
The study was led by Dr. W Ian Lipkin of the Mailman School of Public Health at Columbia University, New York, New York, and is published as an online open access article on 4th September in PLoS One, the journal of the Public Library of Science.
According to MedPage Today, Lipkin told the press:
“We are persuaded that there is no link.”
Many parents in Britain, US and other parts of the world have not vaccinated their children against measles, mumps and rubella (MMR) because they fear there is a link with autism, especially since the 1998 article in The Lancet where a UK team of scientists said there was a link between autism and MMR because they found measles virus RNA in the bowels of a group of autistic children with gastrointestinal disorders.
Since the 1998 study, wrote Lipkin and colleagues in their background information, several studies have failed to find a link between exposure to the measles virus and autistic spectrum disorder (ASD). But public concern may have persisted, suggested the authors, because the studies did not test for evidence of measles virus in the children’s bowels, neither did they examine ASD in relation to gastrointestinal problems, and nor did they try to replicate the original study.
So Lipkin and colleagues carried out a case-control study to find out if children with gastrointestinal disturbances and autism were more likely to have measles virus RNA and/or inflammation in their bowel tissue than children who had gastrointestinal disturbances without autism. They also investigated whether the onset of autism and/or any gastrointestinal disturbance was linked to the timing of receiving MMR.
They took bowel tissue samples (ileal and cecal tissue) from 38 US children who were already undergoing ileocolonoscopy for clinical reasons because they had gastrointestinal disturbances. 25 of the children also had autism, while the other 13 did not (these were age-matched controls).
The tissue samples were tested for presence of measles virus in three separate laboratories that did not know the reason for the test, including one that was involved in the original 1998 study that reported a link between measles virus and autism.
In their analysis, Lipkin and colleagues focused on three points: the order of onset of autism, the onset of gastrointestinal episodes, and the timing of the MMR vaccine. They reported finding “no differences between case and control groups in the presence of MV [measles virus] RNA in ileum and cecum”, and the results were the same across all three laboratories.
“GI symptom and autism onset were unrelated to MMR timing,” wrote the authors, who also found that 88 per cent of the children with autism had behavioral regression. They concluded that:
“This study provides strong evidence against association of autism with persistent measles virus RNA in the gastrointestinal tract or MMR exposure. Autism with gastrointestinal disturbances is associated with elevated rates of regression in language or other skills and may represent an endophenotype distinct from other ASD.”
People with autism spectrum disorders (ASDs) have significant difficulty interacting socially and communicating with others. They also learn, pay attention and react to situations differently to people who do not have ASD, with ability ranging from gifted to severely challenged, according to information from the US Centers for Disease Control and Prevention, whose scientists also took part in the study.
ASD usually starts before the age of 3 and lasts for a person’s whole lifetime. It is four times more prevalent in boys than girls and occurs in all racial, ethnic and socioeconomic groups.
ASDs fall broadly into three types: autistic disorder, pervasive developmental disorder – not otherwise specified (PDD-NOS, including atypical autism), and Asperger syndrome, all of which share symptoms, but differ in terms of onset, severity and characterization. With Rett syndrome and childhood disintegrative disorder, ASDs make up the broad diagnosis category of pervasive developmental disorders.
“Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study.”
Hornig M, Briese T, Buie T, Bauman ML, Lauwers G, et al. 2008
PLoS ONE 3(9): e3140
doi:10.1371/journal.pone.0003140
Open access article published online 4 September 2008.
Sources: Journal article, MedPage Today, CDC.
Written by: Catharine Paddock, PhD