The idea of vaccines causing autism wasn’t a topic I originally planned to cover in this column, mostly because I assumed my fellow students would have the common sense to figure this one out on their own. However, after overhearing a conversation in one of my classes, I realized that the misinformation is absolutely out there, and the anti-vaccine movement is still a very real threat. So this week, let’s talk about the “vaccines cause autism” myth: where it came from, why it’s completely ridiculous, and why people believe it anyway.

Why Vaccines?

Pediatric gastroenterologist Andrew Wakefield and his colleagues published a paper in 1998 which, amid a whole host of unrelated scientific jargon, implied that the Measles, Mumps, Rubella vaccine led to the development of autism in nine young children. If that sample size rings any (statistically insignificant) alarm bells for you, you’re not alone. This paper was met with well-deserved skepticism among the scientific community, and in 2010, the journal retracted the paper and Wakefield lost his medical license.

So why, if Wakefield’s claims are widely considered to be false, do parents continue to believe that vaccines will give their child autism? After Wakefield published his findings, concerned parents looked to him for support after their children began to develop signs of autism soon after being vaccinated. At the time, they largely blamed thimerosal, a mercury-based preservative used in multi-dose vaccines to increase their shelf life. The theory was that mercury is toxic even in small doses, and a mercury-based preservative in vaccines MUST be harmful to their children…right? Actually, thimerosal is ethyl mercury, not methyl mercury. Methyl mercury is toxic to humans, but ethyl mercury is mostly safe, especially in the miniscule doses present in the MMR vaccine. It’s similar to the difference between ethanol (found in whiskey) and methanol (found in wiper fluid) – both are alcohol compounds, but one will kill you while the other just makes you think you can dance. Still, despite scientists’ attempts to placate the public, extensive lobbying drove vaccine manufacturers to stop using multi-dose vials and switch instead to more expensive, thimerosal-free single doses.

The War Wages On

Even after Wakefield lost his medical license, he continued pushing his anti-vaccine message, and many concerned parents were willing to listen. An autism diagnosis, heavily stigmatized, could be a scary thing for parents, and the anti-vaccine movement’s fear-mongering spoke loud and clear to parents who feared having to raise an autistic child. However, their fear was based on myth, not facts. Let’s look at some common myths about autism and vaccines, as well as the actual facts.

Myth 1: Autism didn’t exist before vaccines!

Because thimerosal was introduced into vaccines in the 1930s and autism started being diagnosed in the 1940s, some antivaxxers believe that autism arose as a consequence of mercury exposure among children. Unfortunately, this is a classic pitfall of equating correlation with causation. In addition to thimerosal, the 1930s brought us the Great Depression, World War II, and the first outbreak of grasshoppers in the Midwest. Could it be said that any of these things caused the appearance of autism? Sure, if you have no basic understanding of science or causal relationships.

In reality, autism has existed for far longer than vaccines; we just didn’t have a name for it until the 1940s. Many high-functioning autistic people are able to function well enough that a society with sub-par mental health resources would likely not recognize their disability, or else label them as simply “weird” or “shy.” Children on the lower-functioning end of the spectrum were often thought of as “mentally slow” or possibly cursed by supernatural beings. The idea of the changeling child – a “normal” 3-year-old who is seemingly “replaced” by an emotionless, unresponsive, nonverbal child – may have been an early attempt to explain autism by parents with no scientific background. Additionally, using a postmortem study of behavior, some psychologists have speculated that great minds like Isaac Newton, Stanley Kubrick, and even Albert Einstein might have been on the spectrum. None of these people were ever vaccinated with a dose containing thimerosal.

Myth 2: My child got vaccinated, and now he’s autistic!

This is another example of correlation as causation. Many of the children in Wakefield’s study started showing signs of autism right after being vaccinated. According to their parents, they had had no symptoms up to this point, so their autism must have come from some environmental cause. In reality, parents frequentlydo not notice the early signs of autism in their children, and most children are diagnosed around age 2-3 despite having symptoms beginning at 12 months. Parental self-reports, such as the ones used in the Wakefield study, are notoriously unreliable.

Additionally, even if symptoms do appear following the administration of vaccines, this does not indicate causation. Most vaccines a child receives are administered prior to 12 months of age, when following the CDC vaccination schedule. Coincidentally, autism symptoms typically begin to appear around 12 months of age, becoming progressively worse over the next few years. As mentioned above, this course has been present in autistic children since well before the vaccine schedule was introduced, and the fact that both events typically happen at the same time does not mean that one causes the other. Similar folklore was common in the 1870s, when teething was believed to be a cause of death because many children died at the same age range as when they would teeth. Of course, teething does not kill children – and vaccinations likewise do not cause autism.

Myth 3: Why do we need vaccines anyway? No one dies from measles anymore!

This one is by far the most ridiculous, and also the most dangerous. The reason no one dies from measles anymore is because most people are immune to it. We’ve reached a point that scientists call “herd immunity,” where enough of the population has had the vaccine that the disease is unable to spread. This is important because there are people out there who can’t be vaccinated, due to immune system dysfunctions or other health issues. However, as more people decide not to vaccinate, herd immunity decreases, and diseases are able to spread. A recent measles outbreak in Minnesota was caused by parents deciding not to vaccinate their children, lowering the herd immunity of their community.

Parents frequently decide not to vaccinate their children because of the fear that the MMR vaccine causes autism. But is the possibility of having an autistic child really worth risking measles? Measles is a highly infectious disease, and complications can be fatal even years after infection. Even if the MMR vaccine could cause autism (which, as stated above and by nearly every respectable health professional, it can’t), is the risk of measles really worth skipping the shot? Absolutely not. Autism has never killed anyone, and most people living with autism are able to lead functional, successful lives when they receive proper support. For a child with measles, polio, or smallpox, this is not an option. Vaccines have successfully eradicated some of the world’s deadliest diseases. We can’t set all this progress back because of a myth.