The Science of Causality: Vaccines & Autism
Discerning causes for a disorder such as autism is complicated. To detect rates of autism spectrum disorders (ASD) in certain families, we now use sophisticated technology, such as imaging studies of fetal brain development, genetic screening and behavioral testing. An autistic child will have an ASD sibling about 60% of the time. The genetic connection is also seen in conjunction with structural alterations in the brain and we can diagnose the symptoms much earlier today. ASD is often diagnosed on a behavioral basis, for instance when a child would ordinarily start talking, running and interacting socially. The diagnosis also happens to be around 15 months of age, when many children are vaccinated with the MMR vaccine. But this timing does not mean MMR causes ASD. Extensive studies have examined this and no scientific facts connect the chemical parts of the vaccine to the causes of autism. The desire to understand cause and to make connections is human nature, but coincidental timing is not evidence of cause.
Identifying a cause is a scientific process that we hold to a high bar and we rely on a scientific “jury of peers” to uphold this standard. Unfortunately, a highly publicized event perpetuated myths of harm from the MMR vaccine. A particular scientist, Dr. Ian Wakefield, departed from the scientific method due to his own personal bias and published falsified data in a respected journal in 1998. On the surface it appeared his studies showed that the MMR vaccine triggered both gut and autistic disorders, but his data were later reviewed thoroughly by his British medical peers and they learned that he had manipulated the experimental data. Further, he did so intentionally, falsely naming MMR as the cause of harm to the children he studied. These false conclusions, publicized widely by the lay press are still all over the internet today, perpetuating myths about MMR and other vaccines.
There are many well-informed parents who know their children’s autism is being researched and know that the causes are still not understood today. But a vocal minority is actively publicizing the myth that the MMR vaccine causes autism, when in fact the vaccine is given within 6 months of the time when autism is seen in children’s behavior (about 15 months of age). The timing is a coincidence and newer, validated data show that autistic brain changes occur during the development of the fetus. The anti-vaccination community often says that all vaccines are bad, worse than the diseases they treat and they often present logical fallacies that are easy to see through when you investigate their sources and other beliefs. Anti-vaccine sentiment is often from those who distrust “western” medicine and the pharmaceutical “giants” and they often present a conspiracy theory to state why they discourage vaccination of their own and others’ children.
Someday we will know much more about the gene activation at play in early periods of development in the brain. Further off in the future, we’ll be able to trace the interplay of altered genes and their impact, showing how they cause impaired brain connections and the behaviors we know as ASD. Only with further genetic and neuroscience research will we be able give parents of autistic children a correct reason or “pathway” which can meet the definition of a “cause.” The next step, as in all drug development, will be to learn how to alter that pathway to prevent or treat the altered genes and brain chemistry.
In both chemical drug development and in vaccine development we accept that understanding the pathway is the most difficult part of research, and it is what holds up many new cures. We still don’t understand the pathways at play in HIV/AIDS for instance, and this is why we don’t yet have a vaccine that can prevent the viral infection. As recently as the year 2000, the president of South Africa claimed AIDS wasn’t a viral disease and this attitude delayed the treatment of millions of people with effective medicines (1), resulting in over 300,000 deaths and far more infections. Myths hurt people and so does the diversion of people and policies away from the hard truths.
False interpretations of vaccine science have tragically been broadcasted all over the web (and on TV shows like the Tonight Show and Oprah Winfrey) to millions of people who don’t have a strong scientific background or training in epidemiologic or statistical methods. Health data is hard to understand, but easy to manipulate to feed logical fallacies such as in confusing coincidence with cause. Advanced training in neurodevelopmental genetics and neuroscience is the practice of a few and the few are always easy to marginalize. It’s also easy to distrust the scientists who publish in difficult-to-read journals (I have been reading them for 25 years and they don’t get easier), especially when your child is affected by a serious condition. But this difficulty in communication, combined with the propagation of fear, is the stuff of myths. It’s also a lethal combination and has already caused public health disasters. Just ask the parents of children and adults who contracted whooping cough this past year in the state of Washington (2).
For more information on vaccines, Vincent Racaniello, PhD of Columbia University has established a thoughtful scientific website (3). It is very thorough and he makes all of its content and podcasts freely available for educational purposes. Dr. Racaniello also posts all of the slides from his undergraduate course on virology, which contain many excellent graphs, illustrations, definitions and references.
- Chigwedere P, Seage GR, Gruskin S, Lee TH, Essex M (October 2008). “Estimating the Lost Benefits of Antiretroviral Drug Use in South Africa”. Journal of acquired immune deficiency syndromes (1999) 49 (4): 410–415