Measles vaccine: No association with autism

A new article in the journal PLoS One (link) clearly shows that there is no association between measles virus vaccine and autism. 

The growing public concern over vaccination stems in part from the belief that the measles virus vaccine, given together with vaccines for mumps and rubella (MMR vaccine), causes autism. In the late 1990s it was reported that children with autism spectrum disorders (ASD) had intestinal abnormalities. At the same time, some parents reported that their children began showing signs of ASD shortly after immunization with MMR. When measles virus RNA was subsequently found in the intestine of children with ASD, it was suggested that the measles virus component of MMR was in some way causing autism. The stage was set for parental revolt. 

Since that time, the results of many epidemiological studies have repeatedly shown no relationship between administration of MMR vaccine and ASD. Nevertheless, parent groups have continued to resist the vaccine. The new paper in PLoS One should put this issue to rest. In this paper, the authors examined intestinal tissues (obtained during colonoscopy) from US children for the presence of RNA from measles virus. They obtained samples from 25 children with ASD and intestinal disturbances (such as intestinal pain, gastroesophageal reflux, vomiting, food allergies) and 13 children with intestinal problems but no ASD. The latter 13 samples served as the control group. The authors found no differences between case and control groups with respect to the presence of measles virus RNA in the intestine. Furthermore, there was no relationship between the administration of MMR vaccine and the onset of ASD or enteropathy.

Let’s look at the actual data to better understand the conclusions. First, we’ll compare when gastrointestinal symptoms (GI) or ASD was first observed compared with when MMR vaccine was given. In the children with both ASD and GI, the first dose of MMR vaccine was given at approximately the same time, 15.3 and 16.0 months of age. The first episode of GI problems was at 12 months for ASD/GI children, and at 2 months for GI controls. In 13% of the ASD/GI children, the vaccine was given before the onset of autism symptoms; in 12% of these children, the vaccine was give after the onset of symptoms. From statistical analysis of these data it is concluded that there is no association between administration of MMR and onset of ASD or GI symptoms. 

Measles virus RNA was found in intestinal samples from two children, one from the ASD/GI group, and one from the control group. Clearly the presence of viral RNA is no more likely in children with ASD/GI than in control children. This result contradicts a previous report in which measles virus RNA was detected in 75% of ileal biopsies from ASD children and in 6% of control children.

An hypothesis for induction of ASD by measles virus is that the virus, administered as part of MMR, causes inflammation of the intestine. This condition increases the permeability of the intestine to chemicals that cause ASD. According to this hypothesis, immunization should occur before intestinal symptoms, which in turn should precede ASD. This sequence of events is not consistent with the timing of immunization, GI symptoms, and ASD recorded in this study.

The authors conclude that “the work reported here eliminates the remaining support for the hypothesis that ASD with GI complaints is related to MMR exposure”. We do not yet know the origin of ASD, but this study should now permit resumption of an effective immunization program to prevent measles, mumps, and rubella. If parental objections continue, there will likely be more extensive outbreaks of measles. Given the safety and efficacy of the MMR vaccine, this outcome would be inexcusable.