Vaccines Do NOT Cause Autism

Summary:

This episode was updated in March of 2026 to include systems-level failures to better explain the systems and narratives that keep the debate over vaccines and autism not only alive, but weaponized.

Vaccines don’t cause autism. They cause adults.

In the first episode of her vaccine safety series, Heather tackles one of the most pervasive and damaging myths in public health: the false link between vaccines and autism. With over 30 years of data—and personal insight as both a scientist and a mom—Heather walks listeners through the overwhelming scientific evidence that debunks this myth for good.

You’ll learn how this lie took hold, why autism diagnoses have increased without any rise in actual prevalence, and how anti-vaccine propaganda continues to endanger lives and distract from the real science behind autism. This episode is a clear, compassionate, and fierce call to put facts first—and to protect our kids with the vaccines that save lives.

Listen here or scroll down to read full episode.

Full Episode

Today's episode is a deep dive into vaccines and autism. This episode was updated in March of 2026 to include systems-level failures to better explain the systems and narratives that keep the debate over vaccines and autism not only alive, but weaponized. Text added in March 2026 is green.

Autism and Vaccines.

So this has been an issue for a long time now. In fact, just a little while ago, on February 28th (2025 when this was published) was the 27th anniversary of the shit storm of a paper by Andrew Wakefield that started it all. He falsified data and it was retracted for being fraudulent and he lost his medical license in the UK. There is so much to that horror story that it gets its own episode, I urge you to give it a listen. It will disgust you, but it really explains what started this whole mess. For this episode though, we're gonna focus on the science that shows us without question, that vaccines do not cause autism.

But before we get into that, let me just say, I get it. I'm a mom. For the most part, good parents just want what's best for their kids. And the very loud anti-vax movement uses very effective fearmongering to advance their agenda. And that's why I'm here. When I got pregnant with my son, I was doing research on viruses.

I had heard some things about vaccines that were concerning, so I did what I do best. I investigated it. I read studies, and I talked to experts. And I had a distinct advantage over a lot of people. I not only knew where to go to get the information, I could understand what I read and what I heard, and not just the words, but the statistics and the structures of the studies, and I had access to experts, and that's my privilege, right? At least part of it.

And that's why I'm here to share what I learned with you. The bottom line is all scientific evidence shows that vaccines do not give children autism, and we're gonna talk about it. But this begs the question, if that's the case, then why do people keep saying it does? Well, that is the million dollar question, but I think it boils down to messaging.

There are people with vested interest in the anti-vax movement. They spend a lot of time and money trying to convince people that the lies are true, and they use serious fearmongering to prey on people's uncertainty. And they tell lie after lie about scientists. Right? And so a very deep distrust in scientists and the science that brings us these answers.

Carl Sagan predicted it in The Demon Haunted World: Science as a Candle in the Dark. It's a fantastic book and I really recommend it, but what he warned about in that book, we are living right now, so how do we combat disinformation? Well, that's a topic for another conversation, but there are some things that you can do, especially with regards to conversations about vaccine safety. Always ask for someone's credentials. Why are they qualified to give you this information? Who are they? Don't take their word for it, ask for their sources. Where did they get that information? Just because it jives with something else you heard or believe doesn't mean it's legit. Be willing to question what you thought you knew. The beauty about science is that as we gather evidence, our theories evolve. Our minds are changed. And never be afraid to say you were wrong. It means you learned something.

Before we get deeper into the evidence, Let me explain something. Over the last year, I’ve had more conversations with people who study misinformation, institutional failure, and risk communication—especially around vaccines and public trust. Those conversations made something clear to me: explaining what the evidence shows is necessary, but it isn’t always sufficient.

Parents aren’t just asking whether vaccines cause autism. They’re asking why this claim felt believable in the first place—and why it never seems to go away, even after decades of data. That realization is why I’ve revised this episode. Not to change the science, which is settled—but to better explain the systems and narratives that keep this fear alive.

Ok, back to autism. So, way back in the late 1900s (GenXer here, so that hurts lol) the early 1990s to be exact, we started noticing that the incidence of autism was increasing and it seemed to show up around the same age as children were vaccinated. So we absolutely needed to find out if the one caused the other. And we did! We found out! We now have >30 years of data showing zero correlation between vaccines and autism. In fact, an article was published in 2019 that put this debate to rest. The largest study so far into vaccines and autism, this study concluded there is no link, even in children with a higher risk of developing the disorder. The study, published in Annals of Internal Medicine, looked at 657,461 children born in Denmark from 1999 through 31 December 2010, with follow-up from 1 year of age and through August 31, 2013. They found that children with siblings with autism were seven times more likely to be diagnosed with ASD than children without a family history of the disorder, and boys were four times more likely to be diagnosed than girls. However, even in these higher-risk groups, there was no link between getting vaccinated and being diagnosed with autism. None. As far as science is concerned, this is now a non-issue. This has been shown over and over and at this point the question has been tested so many times that researchers have moved on to studying what actually causes autism.

UPDATE: And this question hasn’t stopped being tested. New large studies continue to analyze vaccination records and autism diagnoses in different populations, and they consistently find the same result. A 2025 study published in Annals of Internal Medicine again found no association between childhood vaccination and autism.

So if the scientific evidence is so clear, why did the fear take hold in the first place?

What this antivax claim gets right — and how it gets misused

Let’s start with the part of this story that feels true to many parents—because dismissing that instinct outright doesn’t help anyone.

The claim gets one thing right: autism diagnoses increased at the same time childhood vaccination expanded.

That timing coincidence is real. And humans are pattern-seeking creatures. When two things rise together—especially when one is emotionally charged—it’s natural to wonder whether one caused the other.

Where this gets misused is in treating temporal overlap as causation, while ignoring everything else that changed during that same period.

Diagnostic criteria expanded. Pediatricians were trained to recognize autism. Schools began offering services that required formal diagnosis. Adults who would never have been identified in childhood were finally being recognized.

Science didn’t ignore this coincidence—it investigated it exhaustively. Large population studies, sibling-comparison studies, genetic analyses, and biologic plausibility tests were done precisely because the question mattered.

What those studies showed—consistently, across countries and decades—is that vaccination status does not change autism risk.

The misuse happens when the emotional power of that early coincidence is treated as evidence, while the actual evidence is dismissed as untrustworthy.

But what about that perceived rise in autism? Let's talk about it.

Was there really an increase in autism? Not really. Not like you might think. But there are some things we need to understand when we look at the statistics. The truth is that there has been an increase in the number of kids diagnosed with autism, while the number of kids with autism has not increased.

Sounds like doublespeak, I know, but hear me out.

It turns out that the difference, based on extensive and well-designed studies, is that rather than an increase in the number of people with autism, we saw an increase in the number of people identified as having autism. The two are not the same. So, previously, there were people on the autism spectrum who were not identified as such; their numbers were not counted. As those people started being identified, it gave the illusion that more people were on the spectrum, but that wasn't the case. It means we are now finding and identifying those people and counting them. They were there before we counted them. Make sense?

This happened for a number of reasons. First, physicians began looking for autism. If they looked for it and found it, they diagnosed it. Before the 1990s we weren't looking for it, so all but the most severe cases went undetected and undiagnosed. Not only that, but the diagnostic criteria for autism changed - it became a spectrum disorder - that then means that children who would not have met the previous criteria for autism, but who fall on that spectrum, are now diagnosed as having autism. This alone dramatically increases the number of children diagnosed with autism. So now we are looking for it, the criteria to be given the diagnosis has changed, and finally, it's being recognized as something that kids can get help for in school, so parents are more willing to look for and accept the diagnosis, even when the child is on the very mild end of the spectrum. Again, this increases the number of kids diagnosed with autism.

When you take all the data on children with autism or on the spectrum, from 1990-2010 we find: "In 2010 there were an estimated 52 million cases of ASDs, equating to a prevalence of 7.6 per 1000 or one in 132 persons. After accounting for methodological variations, there was no clear evidence of a change in prevalence for autistic disorder or other ASDs between 1990 and 2010." That is from The epidemiology and global burden of autism spectrum disorders. Another excellent and easier to read article is The Real Reason Autism Rates are Up in the US.

Since 2010, autism spectrum diagnoses have continued to rise and for the same reasons. Now though, it's more related to people who weren't diagnosed as children. A paper published in JAMA late last year suggests that for some, ASD may be going undiagnosed in childhood, and only getting recognized in early adulthood when challenges in daily life become unmanageable. There has been no drastic increase in autism. There's been an increase in identifying people of all ages who are on a very wide spectrum. And large genomic studies now show autism is strongly influenced by genetics, with heritability estimates between roughly 70 and 90 percent.

So that's the explanation. And that timing coincidence is actually where the entire vaccine–autism fear began.

And we are left with the glaring fact that studies by dedicated, hardworking scientists many of whom are parents, show over and over that vaccines don't cause autism. If you need more convincing check out the Autism Speaks website. They also do a great job providing links to the evidence I've talked about. You truly can rest easy and protect your children because Vaccines do not cause autism. And yet, despite all this evidence, the claim refuses to die.

What would have to be true for this conspiracy to work

Now let’s pause and ask a grounding question: what would have to be true for vaccines to cause autism, and for that fact to be successfully hidden?

• First, autism would need a biologic mechanism tied to vaccination that produces consistent, measurable effects. Despite decades of research, no such mechanism has ever been demonstrated.

• Second, population-level data from dozens of countries—many with public healthcare systems and no pharmaceutical profit motive—would all have to be wrong in the same way, year after year.

• Third, removing suspected components like thimerosal would have had to reduce autism rates. It didn’t.

• Fourth, scientists, clinicians, epidemiologists, and autistic researchers themselves would all have to be complicit in hiding the truth—despite strong professional incentives to be the person who discovers a real cause.

That level of coordination isn’t just unlikely—it’s incompatible with how science actually works.

What is compatible with reality is something much more mundane: a frightening coincidence, amplified by poor communication, exploited by bad actors, and sustained by institutional failures to explain uncertainty clearly and early.

But online echo chambers are still spreading disinformation. People with a financial stake in the antivax movement, including Andrew Wakefield, are still spreading lies about vaccines. Wakefield and a co-author were stripped of their medical licenses. After the extensive investigation, The Lancet formally retracted the paper in 2010 and Wakefield was struck off the UK's medical register. He disappeared to Texas and people pay him to speak at anti-vax events and make propaganda films furthering their agenda. In Feb 2024 he premiered the trailer for his first feature film Protocol-7, at the Autism Health Summit in San Antonio. The film claims the mumps vaccine causes serious long-term health issues. WHICH IS A LIE. Spoiler: he was never anti-vax. His entire agenda back in the day was to disparage the MMR vaccine formulation, because he had his own patented formulation and he wanted to sell it. He was never antivax until it was the only way he could earn a living. He hurt kids to do it, too.

Can you see why it's upsetting?

Where the system failed — and what it would take to fix it

This is where the conversation usually breaks down—not because parents are unreasonable, but because institutions often are.

The system failed in several key ways.

First, scientists underestimated how powerful timing-based fear would be. The early rise in diagnoses wasn’t accompanied by clear, accessible explanations of why that rise was happening.

Second, public health messaging focused on conclusions, not process. Parents were told “there’s no link,” without being shown how that determination was made, what was tested, or why certain explanations failed.

Third, bad-faith actors were allowed to frame themselves as the only ones asking hard questions. That vacuum let fear masquerade as skepticism.

And finally, institutions were slow to acknowledge uncertainty early on, which made later confidence feel dismissive rather than earned.

So what would it take to fix this?

It would take:

• explaining how science rules things out, not just what it concludes

• being honest about uncertainty while evidence is still emerging

• responding faster and more visibly when claims are debunked

• and treating parent concerns as legitimate questions, not obstacles

None of that requires lowering scientific standards. It requires better communication—and accountability when communication fails.

So we know vaccines don't cause autism. There are some really loud voices out there working to convince parents that autism is from vaccines. Or that vaccines are just unsafe and turn you into reptiles or or who knows what. The fearmongering doesn't stop. But the truth is that they are using fear to advance their own agendas. The two biggest problems with the anti-vax movement are that in addition to putting lives at risk from preventable infectious diseases, they make it really hard for scientists to work on the real problem. 

And today, misinformation spreads differently than it did in the 1990s. Algorithms amplify emotionally engaging content, which means frightening stories travel farther and faster than careful scientific explanations.

You may think I have an agenda too, and I do. I am trying to help parents make informed choices that will protect their children. I know what's it's like to be a mom and to hear these things and wonder what's the right thing to do? And that's why I'm here. I'm here because I ge really frustrated at the misinformation that's out there and I can't keep my mouth shut. So here I am. One of the things I like to say is that the antivax movement is a luxury provided by safe and effective vaccines. Pretty much everyone who is antivax grew up vaccinated, and safely vaccinated at that, and never experienced horrifying epidemics where corpses were being burned in the streets. They never had to see family members or friends in iron lungs because of polio. And you know damn well RFKjr's children are fully vaccinated. Just think about that. Yet, here we are.

Right now there's an ongoing measles outbreak in west Texas (as I'm typing this it's March 16, 2025). At this time, 259 cases have been identified since late January. Thirty-four of the patients have been hospitalized and one unvaccinated 6 year old Mennonite girl has died so far. It's ongoing and will only get worse. Check out my measles episodes for more details on the disease, the virus, and the vaccine. The total cases across the US have already surpassed the entire total for last year.

Update: A year later, the outbreaks have not gone away—they’ve expanded. The U.S. has now recorded more than 1,300 measles cases across more than 30 states in 2026 alone, with major outbreaks including one in South Carolina. More than 90% of infections are in people who are unvaccinated or whose vaccination status is unknown. The 2025 total case count was 2,284.

Surviving measles also comes with a cost. Measles can lead to serious long term health problems. One of the most severe is called subacute sclerosing panencephalitis (SSPE), which is a very rare, but fatal disease of the central nervous system that results from a measles virus infection. SSPE generally develops 7 to 10 years after a person has measles, even though the person seems to have fully recovered. The risk of developing SSPE is higher for a person who gets measles before they are two years old.

Other severe complications include pneumonia and encephalitis (swelling of the brain). Patients may need to be hospitalized and could die.  As many as one out of every 20 children with measles gets pneumonia, the most common cause of death from measles in young children. About one child out of every 1,000 with measles will develop encephalitis that can result in convulsions, deafness, or intellectual disability. And finally, for every 1,000 children with measles, one or two will die. There was a reason the measles vaccine was a game changer for parents when it first came out. It saved lives. Anti-vax propaganda is exactly why we are seeing frightening increases in measles. 95% of those currently sick with measles are unvaccinated.

We are also still in the middle of flu season. Ten pediatric deaths were reported this week, bringing the 2024-2025 flu season total to 57 pediatric deaths. CDC estimates that there have been at least 24 million illnesses, 310,000 hospitalizations, and 13,000 deaths from flu so far this season.

Update (2026): The 2026 Flu season has been even worse. At least 27 million flu infections, 350,000 hospitalizations, and roughly 22,000 deaths this season in the U.S. More than 100 children have died, and about 85% of those children were not vaccinated. That's almost twice as many as last year and last year was considered really bad.

Am I fearmongering too? Maybe, and I'm sorry for that. Well, sorry not sorry. In this case, the danger is all too real. Just ask the mom mourning her child in Texas.

One more thing I'd like to convey. In 2017, after his first inauguration a letter was written to trump and signed by 9 pages of scientific organizations, asking him to speak out in favor of vaccines, to help curb the anti-vax movement. He didn't, of course, but I linked it in the original blog post because after the 9 pages of signatures, there are 18 pages of studies - summaries and links - that all show that vaccines do not cause autism. They are powerful evidence of the truth about vaccines. The link now leads to nothing. The letter was removed from that website. Removing access to scientific information is dangerous. But I got the letter. So I'm pasting it here for you. It's a ton of evidence, even before the 2019 or 2024 studies, showing vaccines do not cause autism.

Vaccine_Safety_Letter_020717.pdf

Download PDF • 315KB

I want to be clear about one thing. I understand why this fear took hold. I understand why it persists. And I understand why parents keep asking this question.

But understanding fear doesn’t mean feeding it.

The evidence tells us vaccines don’t cause autism. The harder—and more important—work is explaining why that evidence deserves trust, and how systems failed to earn that trust sooner.

That’s why I revised this episode: to make that distinction clearer, and to give parents better tools than fear ever could.

Vaccines don't cause autism, they cause adults.

You have to check out the episode on Wakefield so you understand how this started. It's all there. Bottom line is please don't take someone's word for something this important. Even mine. I link all my sources. They are there for your scrutiny. I'm a virologist and mom who wants to protect her son. To do that best, I make sure he's vaccinated. I hope you do the same.