No, Vaccines Don’t Cause Autism

Parents want to do right by their kids. We want to keep them healthy. Keep them safe. Help them to lead their best lives.

So, when you hear that chatter about vaccines causing autism, you might be tempted to take it to heart. You love your kiddo. You want what’s best for them. And those so-called experts on social media can sound like they know what they’re talking about sometimes.

Fear not: Major research studies (the kind you can trust) have definitively proven that vaccines do not cause autism. Period. End of story.

But why does the myth persist?

We talked with pediatrician Kristin Barrett, MD, about what the best scientific research has to say about vaccines and autism.

Vaccines and autism: The science

The suggestion that vaccines cause autism can be traced back to the 1990s. Since then, researchers have worked tirelessly to determine if there’s a connection. And have proved time and again that there isn’t.

It started in 1998. Then-doctor Andrew Wakefield created a stir when he published a study claiming to have found a connection between autism and the MMR (measles, mumps and rubella) vaccine.

In the years to follow, that paper was widely discredited. The journal rescinded the study (the academic equivalent of a public walk of shame). And Wakefield lost his medical license.

The problem? The paper was found to be fraudulent. The results were flat-out false. And the science behind them? Wouldn’t even stand up to the scrutiny of a middle-school science fair.

“He was making claims that weren’t supported by his study,” Dr. Barrett shares. “For example, Wakefield was trying to prove the MMR vaccine could cause intestinal inflammation, which could lead to proteins and viruses leaking into the body and cause autism. But one major flaw was that many kids in the study didn’t actually exhibit intestinal symptoms until after they were diagnosed with autism. There was no line connecting the vaccine to intestinal inflammation, and therefore, autism, at all.”

What’s more, the sample size was tiny. The study looked at just 12 kids. Not nearly enough to learn anything concrete from.

The cherry on top? We now know Wakefield was funded by lawyers who were representing families who had filed lawsuits against vaccine manufacturers. He never disclosed his financial interest in the matter.

“Even many of the co-authors on Wakefield’s studies have redacted their findings,” Dr. Barrett points out. “They’ve publicly come out and said, We don't agree with this.”

And yet, the headlines were splashy. The results terrified parents. The damage was done.

In the years since, scientists have worked relentlessly to determine if there was, in fact, something there. To thoroughly test whether vaccines could be playing a role in the uptick in autism diagnoses we’ve seen in the past few decades.

Their findings underscore that there is no connection between autism and vaccines.

One of the biggest studies to confirm that vaccines don’t cause autism was published in April 2019 in the Annals of Internal Medicine. The researchers studied more than 650,000 children born between 1999 and 2010.

“They compared the rates of autism between children who received the MMR vaccine versus those who didn’t,” Dr. Barrett reports. “They found no increased risk of autism in the vaccinated group. In fact, the vaccinated group had a slightly lower incidence of autism.”

The difference wasn’t so great as to suggest that MMR vaccines could in any way protect kids from autism. But the results certainly prove that MMR vaccines aren’t causing autism.

Another large study looked specifically at kids who were at increased risk for autism. Such as those who had an autistic sibling. Could vaccines further increase their risk?

Nope. That study concluded there was no difference. Vaccines didn’t increase rates of autism even in high-risk kids.

What causes autism?

Time and time again, high-quality, reliable scientific studies have shown that vaccines don’t cause autism.

But what does? Unfortunately, that’s not as well understood.

“Autism is on the rise, and we can’t give families a clear answer of why it’s happening. So, it does lead to some grasping at straws,” Dr. Barrett acknowledges. (Hence, the vaccine myths continuing to be batted about.)

About 1 in every 36 kids in the U.S. is autistic. And there are a lot of theories about what causes autism.

We know that autism can have a strong genetic component. And some studies suggest that environmental factors are associated with autism. That may include things like:

• Becoming pregnant over age 35
• Having gestational diabetes
• Certain complications during birth

What’s more, some theories suggest that the rates of autism itself aren’t actually increasing (or increasing drastically). It’s just that we now understand the condition more fully. That means more people being diagnosed who would have been missed in prior generations.

But all three are likely at play.

“The increase we’re seeing in autism is probably a combination of genetic factors and environmental factors in addition to the fact that we are doing better at identifying it and labeling it,” Dr. Barrett advocates.

Importance of immunizations

Vaccines are the absolute best way to protect your kid from devastating diseases — during their childhood and throughout their life.

“All of the diseases we vaccinate for are real diseases that still exist in the world that can cause serious, long-term disabilities and can even — in the worst cases — cause death,” Dr. Barrett emphasizes.

Being unvaccinated can leave your child susceptible to these very preventable conditions.

Vaccines can be so successful that they can completely eradicate the disease in highly vaccinated regions. That’s why we don’t see rubella or diphtheria in the U.S. anymore.

But there’s a catch.

“As demonstrated by measles, if we don’t continue to vaccinate against these diseases, we can see resurgences after they had previously been eradicated,” she warns.

That’s because high rates of vaccination in the population cause what’s called “herd immunity.” Enough people are immune to the disease to keep it from spreading.

If the rates of vaccination drop, we lose that protection. Meaning that people who can’t get vaccinated — including newborns who are too young for vaccines and people who have certain medical conditions — will be at significant risk.

Consider this: Before widespread immunization, about 400 to 500 people died each year from measles.

“95% of people need to be immunized against measles to achieve herd immunity and prevent an outbreak,” Dr. Barrett states. “There are places in the U.S. right now where vaccination against measles is dropping into percentages in the 80s. So, we are coming into a time where we could be seeing more and more measles outbreaks.”

And measles is highly contagious. About 90% of people who come into contact with the virus will become infected if they aren’t vaccinated.

But what about that vaccine schedule? Some people are concerned that babies and little kids get too many vaccines over too short a period.

Dr. Barrett recommends considering the fuller context. “Babies’ immune systems are perfectly primed to take in all of these new antigens at once. I promise you, the viruses and bacteria that they’re being exposed to in those initial vaccine visits is nothing compared to the antigens they would be exposed to in a single trip to the supermarket.

“They’re being exposed to thousands of new things every single day. So, the few that we vaccinate them for is really a blip on the radar.”

The evidence is clear: Vaccines save lives. And they do NOT cause autism.