By: Erin Thomas
The question on everyone’s minds…
With an astounding incidence of autism in the U.S. today that only seems to be growing, it is even more astounding that a definite cause has yet to be found. Autism has done a successful job of leaping into the public eye and vernacular; fifteen years ago, talk about having an autistic child likely would have been met with confused gazes. It is understandable that the lack of an explicit cause is a frustrating reality for so many individuals on the Autism Spectrum and their families. Without a cause, it becomes all the more difficult to target a treatment for an individual, and families are often left shooting in the dark for therapies.
One school of thought that has pervaded the media is the connection between the Measles-Mumps-Rubella (MMR) vaccine and autism. You may have heard public figures, most notably Jenny McCarthy, promoting the culpability of MMR as a cause of autism. Well, from a scientific standpoint, you may be surprised to hear that there has been NO scientific evidence to support this claim. Not one. So how did this idea gain fuel and become so embedded in the public perception of autism?
Quick history break- Well in 1998, a gastroenterologist named Andrew Wakefield published a paper in Britain describing 8 children who apparently experienced the onset of autism one month after receiving the MMR vaccine. Wakefield claimed that the MMR vaccine caused intestinal inflammation that allowed certain peptides (chains of two or more amino acids, similar to proteins but normally smaller) to enter the bloodstream and thus make their way to the brain where they affected development (Gerber, Offit, 2009). Wakefield was eventually prompted to take down his paper because of the
- lack of experimental controls to confirm that MMR was responsible for causing the autism
- the unsystematic method in which data was collected
- the lack of connection between measles, mumps, or rubella to intestinal inflammation, and
- the fact that gastrointestinal issues did not even precede autism onset in some children. (Click here to read more about the issues nullifying the Wakefield paper.)
Since then, research has been conducted to further rule out MMR’s role in causing autism. For one, research has not determined that children with ASDs contain more of the genetic information of the measles vaccine virus than those without ASDs (Hornig, 2008). Moreover, the harmful peptides Wakefield suspected to have been invading the brain from the intestine have not been identified (Gerber, Offit, 2009). In fact, the proteins now believed to contribute to ASDs are endogenous, or have no external origins, and affect neuron activity (Sutcliffe, 2008).
Studies have further severed the link between the MMR vaccine and autism by showing that the incidence of autism has not increased since people started becoming vaccinated against MMR. An extensive study on 498 autistic children born from 1979-1992 in the UK is just one source of evidence that rates of autism did not increase after the introduction of the MMR vaccine in 1987. Nor did children who received the MMR vaccine or a second dose of the vaccine have higher onsets of autism than unvaccinated children (Farrington, 2001). Click here for an outline of more studies that have refuted the connection between MMR and autism.
So if there is no scientific evidence supporting the link between the MMR vaccine and autism, and no logical scientific mechanism for how MMR could even lead to autism, why is the idea still lingering in the minds of parents taking their newborns to the pediatrician’s office?
The MMR vaccine is administered in babies at 18 months…right around the time when autism is typically first detected (although in some cases it can now be detected earlier). Scientists have coined the term “correlation vs. causation” to illustrate an important fallacy associated with the connection being made here. For example, if I notice that the number of sick people in the U.S. increases as the consumption of hot chocolate in the country increases, is it safe to say that drinking a sweet cup of Swiss Miss causes people to fall ill? Of course not! The two are simply correlated because people happen to consume more hot chocolate in the winter, which is when flu season is at its peak. Similarly, the correlation between the administration of MMR vaccines at 18 months and the subsequent diagnoses of autism around that time does not necessarily link the vaccine to the cause of autism. This correlation vs. causation issue is something we will keep in mind as we continue to assess ongoing autism research.
Farrington CP, Miller E, Taylor B. MMR and autism: further evidence against a causal association. Vaccine. 2001;19:3632–5. 
Gerber J, Offitt P. Vaccines and autism: a tale of shifting hypotheses. Clinical Infectious Diseases. 2009;48:456–461 
Hornig M, Briese T, Buie T, et al. Lack of association between measles virus vaccine and autism with enteropathy: a case-control study. PLoS ONE. 2008;3:e3140.
Sutcliffe JS. Genetics: insights into the pathogenesis of autism. Science. 2008;321:208–9. [PubMed]