Chances are, you’ve heard the idea that vaccines can cause autism. This notion is championed by various organizations and individuals; one of the most prominent is actress Jenny McCarthy, whose son was diagnosed with autism at age 2. She has an autism-related organization called Generation Rescue, and on its website is a guide to vaccine safety.
I was a bit surprised by how relatively toned down it was, but I got more of what I expected at one of the sites it directed people to for more information, the National Vaccine Information Center. It includes a “cry for vaccine freedom wall” and a “vaccine victim memorial”. They have a database of people’s reported adverse reactions to vaccines, and a search for autism spectrum disorder yields 391 case reports. One thing that struck me was the seemingly random grab bag of multiple symptoms/conditions that were also being attributed to the vaccine at the same time in these case reports.
The origins of anti-vax
So where did this idea come from that autism can result from vaccination? In 1998, the prominent medical journal The Lancet published an article by Dr. Andrew Wakefield and 12 other scientists that looked at 12 children who had bowel disorders and autism. It stated: “Onset of behavioural symptoms was associated, by the parents, with measles, mumps, and rubella vaccination in eight of the 12 children.”
However, in 2004, 10 of the original 12 authors published a retraction in The Lancet of their interpretation of the results of the 1998 study, including the link between MMR vaccine and pervasive developmental disorder. In 2010, The Lancet retracted the published article entirely, stating that parts of it were incorrect or blatantly falsified.
In 2010, the UK General Medical Council found that Andrew Wakefield had committed scientific dishonesty and breach of duty, and was “guilty of serious professional misconduct”. For several reasons, including his “wide-ranging transgressions” and “disregard for the clinical interests of vulnerable patients”, his name was erased from the Medical Registry, an extreme action that they justified in part by his lack of insight. Clearly, this is not an individual whose ideas should be considered credible.
Multiple studies show no link
A 2007 paper in Current Opinion on Infectious Diseases dismissed papers linking autism and MMR vaccine as “not scientifically stringent” and having “serious methodological limitations. A 2007 article in The New England Journal of Medicine addressed concerns about thimerosal, a vaccine preservative that contains small amounts of mercury well within the World Health Organization’s acceptable limits. The article concluded that the baseless association between thimerosal and autism “has given rise to a cottage industry of charlatans offering false hope, partly in the form of mercury-chelating agents.”
A 2014 paper in the journal Vaccine found no relationship between autism and vaccination in general, and specifically MMR vaccine, thimerosal, or mercury. A 2010 article in Clinical Infectious Disease stated that:
“Twenty epidemiologic studies have shown that neither thimerosal nor MMR vaccine causes autism. These studies have been performed in several countries by many different investigators who have employed a multitude of epidemiologic and statistical methods. The large size of the studied populations has afforded a level of statistical power sufficient to detect even rare associations. These studies, in concert with the biological implausibility that vaccines overwhelm a child’s immune system, have effectively dismissed the notion that vaccines cause autism.”
Facts aren’t enough?
Yet the overwhelming evidence hasn’t been enough to convince the anti-vaxxers. Part of the problem is that children can begin to show signs of autism around the time they’re getting some of their childhood vaccinations. People may mistakenly assume that just because something is temporally correlated (occurring at the same time) there must be a cause and effect relationship. This kind of thinking is fundamentally flawed, and anyone with some degree of research literacy knows that correlation and causation are not the same thing.
This matters because in an unreasonable attempt to avoid autism, parents aren’t vaccinating their kids, which puts other people at risk. Certain individuals can’t get vaccines for medical reasons, including a compromised immune system, and this is where the concept of herd immunity becomes particularly important. Herd immunity refers to the idea that if a high enough percentage of the population is vaccinated, an infectious organism has a hard time moving through the population, which serves to protect those who aren’t vaccinated.
The percentage of the population that must be vaccinated depends on how contagious the infectious agent is; for a highly infectious illness like measles, 90-95% of people must be vaccinated to achieve herd immunity. If the anti-vaxxer movement gains enough steam, this means some of the most vulnerable members of the population may suffer.
Imagine how much good could be done if all the energy and money that goes into anti-vaxxing could be diverted into better understanding autism spectrum disorders and how parents of neurodiverse kids can help them thrive.
There’s more on pseudoscience and public health on The Science Corner.The Science Corner: Debunking Pseudoscience