Because you can never have too many reminders of these facts, here’s how we know that autism is not caused by vaccines. 

The paper that started it all

Vaccine skepticism has existed for as long as we’ve had vaccines, but this specific fear around autism was first sparked by a 1998 paper published in renowned medical journal The Lancet. 

The paper, which was eventually retracted (though it took 12 years), alleged a link between gastrointestinal illness and neurodevelopmental symptoms indicative of autism in a small group of children.

At a highly unusual press conference announcing the publication, first author Andrew Wakefield made explosive comments suggesting that routine measles, mumps, and rubella (MMR) shots could have been responsible for causing autism in these kids. This is despite the fact that the original paper actually contains the sentence, “We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described.”

The controversy

Almost immediately, fellow scientists and experts began to raise serious concerns about the quality of the data in the paper and its conclusions, with many questioning how it was published in the first place.

As Julia Belluz wrote for Vox in 2019, the sample size was an immediate red flag. Only 12 kids were included in the study. Brian Deer, one of the few investigative journalists who sought to dig deeper into Wakefield’s claims at the time, found evidence of data falsification and exaggeration, with parents of the children confirming that the paper contained incorrect medical information about them. 

It took several years, but in 2008, Wakefield and two of his co-authors were called before a General Medical Council (GMC) disciplinary panel. The GMC is the body that maintains the official register of medical practitioners in the UK. Someone who is found to have seriously breached their professional codes of conduct can be “struck off” the register and have their license to practice medicine revoked. 

In 2010, this is the fate that befell Wakefield. As the Guardian reports, the GMC said at the time, “The panel is profoundly concerned that Dr Wakefield repeatedly breached fundamental principles of research medicine.” As well as the allegations of data fraud and undisclosed financial conflicts of interest, the panel heard how the Wakefield’s team subjected some children to invasive procedures that were not medically necessary, and that had not received ethical approval.

Some hoped this, as well as the retraction, would be the final nail in the coffin for the MMR-autism scare. 

“Why The Lancet published it is completely beyond me,” said pediatrician Dr Suzanne Lewis, speaking to the Canadian Medical Association Journal in 2010. “The risk-versus-benefit equation was really tipped the wrong way by this research that was so egregious.”

The thing that’s important to understand is that essentially all of the fear was based on just this one paper. Wakefield and co-authors never replicated their findings. 

They did publish a follow-up in 2002 that claimed to find measles virus in the intestinal tissue of autistic children at much higher rates than in their non-autistic peers. This paper, too, was riddled with methodological flaws. For one thing, the authors seemingly made no effort to distinguish between measles virus from a vaccine and virus that the kids had been naturally exposed to.

On the other hand, by 2010 there had been a slew of other scientific studies debunking any supposed link. It’s not as though there was an equal body of evidence on both sides of this argument. 

The evidence against the MMR-autism link

At time of writing, the Wakefield paper ranks eighth on Retraction Watch’s list of highly cited retracted papers, with the majority of those citations coming after it was retracted. Many of those citations come from reviews and studies on attitudes to vaccines and the spread of misinformation, highlighting the far-reaching consequences of Wakefield’s comments in that press conference all those years ago.

Many better designed and higher quality studies have investigated the supposed association between vaccinations and autism, and the overwhelming consensus from them is that no link exists. 

One of the best-known came in 2002 from Danish researchers, who studied over 500,000 children, 82 percent of whom had received routine MMR vaccination. Their results were clear: “There was no association between the age at the time of vaccination, the time since vaccination, or the date of vaccination and the development of autistic disorder.”

Similar results were reported in a study published just a year after the Wakefield paper – and in the very same journal. Focusing on autistic children across eight health districts in one region of England, the team was unable to find any difference between vaccinated and unvaccinated kids, and no association between the timing of the vaccine and the onset of signs of autism.

A further study by the same first author, Professor of Community Child Health Brent Taylor, looked into the claims around autism, MMR, and bowel issues, and concluded, “These findings provide no support for an MMR associated ‘new variant’ form of autism with developmental regression and bowel problems, and further evidence against involvement of MMR vaccine in the initiation of autism.”

A 2015 study in the Journal of The American Medical Association found no increase in autism rates in kids who had received one or two doses of the MMR based on almost 96,000 children, including some with older siblings who had already received an autism diagnosis.

Another study from Denmark published in 2019 – which was, at the time, the largest of its kind – replicated the finding that there was no link between autism and vaccination.

And a 2020 Cochrane review of 138 studies found that both the MMR and a newer version of the vaccine that also immunizes against chickenpox were safe, effective, and not associated with autism. 

These are just a handful of studies from a huge body of evidence that amounts to a pure and simple truth: there is no scientific reason to believe that vaccines and autism are linked.

The genie was out of the bottle

However, as they say, mud sticks. Wakefield’s comments back in 1998 went largely unchallenged in the popular press, sparking a panic in his home country of the UK that saw many parents refusing the MMR vaccine for their children. 

These fears soon spread around the world, leading to mass mistrust of a vaccine that had been safely in use for a decade. The ensuing research repeatedly showing no association between the MMR vaccine and autism did not reach those people in the same way.

One widely held fear centered around the alleged presence of mercury in vaccines. The only mercury that was ever present in any vaccine was in the form of ethylmercury, contained within a preservative called thimerosal. As the Centers for Disease Control and Prevention (CDC) points out, ethylmercury is not hazardous to human health in the same way as other forms of mercury, and the MMR vaccine never contained thimerosal to begin with.

Another part of the problem is that vaccines became a convenient scapegoat for parents who were observing changes in their kids’ behavior and, understandably, were looking for answers. 

Signs of autism first tend to become apparent in children when they’re around 12 to 18 months of age. Prior to that, a child can appear to be following a typical developmental trajectory. This is also the age at which the first dose of MMR is recommended. 

The coincidence of this timing has led many a parent to blame a recent MMR shot for alterations in their child’s behavior that appear to have come on suddenly.

But, as we’ve hopefully shown, it is just a coincidence.

“The leading ‘fake expert’”

On a scientific level, the supposed MMR-autism link is one of the easier claims to debunk. There’s so much evidence against it, including analyses that meet the gold standard for quality medical research such as the Cochrane review. 

Wakefield himself, the architect of the scare, has been roundly discredited, both personally and professionally. However, he still continues to tout health-based misinformation to a dedicated audience.

“Today, he is considered the leading ‘fake expert’ who still makes a significant profit from the publicity and from public appearances that have nothing to do with medicine and science,” epidemiologist Senad Begic told UNICEF young reporter Emir Dresevic.

The CDC estimates that before measles vaccines were available, up to 500 people died each year from the disease, 48,000 were hospitalized, and 1,000 experienced the severe complication of measles encephalitis (swelling of the brain) – and that’s just in the US. 

People may lazily describe measles as a “childhood disease”. What that fails to account for is the number of children who died or were left with permanent health consequences as a result of their infection. 

Vaccines changed all of that, just as they’ve saved millions of lives by protecting populations from other killer diseases like polio, diphtheria, flu, COVID-19, and now even cervical cancer. In 2000, the US had eliminated measles; today, thanks to vaccine hesitancy seeded by overblown, inflammatory claims based on fraudulent data, the disease is having a resurgence. And it doesn’t have to be this way. 

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current. 

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.