Vaccines Can Cause Autism: Causation vs. Correlation

Many doctors refuse to point a finger at vaccines when a child is clearly harmed after being vaccinated.

Do vaccines cause autism? This question has been the source of a heated debate for a long time. While researching autism for the last six years, I’ve often seen articles about causation and correlation. Although I am a layperson who doesn’t completely grasp the scientific process, I have to say the topic intrigues me. I’m going to, if you will, think out loud in this article. Bear with me, and if you have ideas you’d like to share, please do.

First of all, what does causation mean? What is correlation? Merriam-Webster defines “causation” as:

a: the act or process of causing
b: the act or agency which produces an effect

I’ll come back to correlation in a moment. With this definition of causation in mind, there seem to be three possible answers to the question, do vaccines cause autism?

1. Yes. Always.
2. No. Never.
3. Maybe. Sometimes.

Let’s explore each one.

Yes. Always.

I don’t think anyone believes that vaccines always cause autism. That would mean that every child who gets a vaccine ends up with autism. It just goes against reason and logic—and it’s simply not true. There are a lot of children who have gotten a lot of vaccines, and they don’t have autism.

No. Never.

“Never” is a strong word. It would mean that no child has ever gotten autism because of a vaccine. Not one single child. This option is as unreasonable and illogical as the “Yes. Always” option.

Maybe. Sometimes.

I think any reasonable, logical person would find this option … well, reasonable and logical. Vaccines sometimes cause autism. Not always. Not never. Sometimes. Like cigarettes and cancer. It’s an accepted scientific fact that people who smoke have a higher risk of cancer. But there are people who smoke for a lifetime and don’t get cancer. Then, there are people who never smoke and end up with cancer. Sometimes.


Back to option #2, No. Never. This is where correlation comes in. If this option were true and vaccines never cause autism, for every child whose parent claims he or she developed autism after a vaccine, there is another explanation in the scientific world: correlation. According to M-W, “correlation” is:

the state or relation of being correlated; specifically : a relation existing between phenomena or things or between mathematical or statistical variables which tend to vary, be associated, or occur together in a way not expected on the basis of chance alone

Correlation doesn’t necessarily imply causation. But think about these examples:

1. A child runs out in the street, is hit by a car, and dies. Did the car correlate with his death, was it responsible for his death (causation), or both? Obviously, the car correlated with the child’s death because the two events occurred almost simultaneously. Most reasonable, logical people would say that being run over by the car caused the child’s death. So, there was correlation and causation. A skeptical person might say the child was on the verge of a heart attack (or some other fatal event) in the moments before he was hit by the car, so the car correlated with his death but didn’t cause it. Cause of death could have been the heart attack, and the car just happened to hit the child at almost the same time.

2. A child gets a vaccine and then develops a low-grade fever—a known, undebated side effect of the vaccine. Or redness at the injection site—another known, undebated side effect. Since the fever or redness occurred at about the same time the child got the vaccine, the vaccine also correlated with those side effects.

3. A child gets a vaccine and then gets a fever of 102 (not low-grade), has a seizure, gets sick, stays sick, and—you know the rest. Autism. According to diehard pro-vaxers, the vaccine could not be the cause of the autism. The vaccine simply correlated with the autism. Perhaps the more immediate the adverse event—say, the child dies within minutes or hours of receiving the vaccine—the more likely causation might be. Again, I’m thinking out loud here. Maybe the greater the time between the vaccine and the adverse event—say, the child regresses over a period of weeks or months—the greater the possibility that there could be other causes. Maybe, for instance, the child was on the verge of a seizure disorder and it was just a matter of time before he had the first one. Or he had “inherited” autism, and it was just a matter of time before the first symptoms appeared. Correlation but no causation. Personally, I don’t see how any reasonable, logical person could completely rule out the vaccine as at least a contributing cause—if not the only cause.


You may remember the article I published last month, “1 in 88: What’s Causing the Increase in Autism?” I mentioned some of our government’s proposed causes of autism. Living within three miles of a freeway is one. I’m not saying that isn’t possible. Maybe it is one cause. One of numerous. But how could it be proven? How is it not just correlation? In addition to living close to a freeway—and I’m thinking like the CDC now—maybe these kids’ moms took certain medications when they were pregnant, maybe their moms and/or dads were too old, maybe the mom gained too much weight, maybe the child wore pajamas with flame retardant in them, maybe the baby was premature or inhaled household cleaners or too much dust in utero. Etc. Etc.

When I ponder causation and correlation, the Danish study that was published in 2003 comes to mind. The claim was that even when mercury was removed from most vaccines (which is, of course, not the case), the autism rate did not decline. In fact, it increased. The conclusion: Mercury doesn’t cause autism. How scientific is that? It doesn’t prove that vaccines don’t cause autism. Even if the findings were true as reported (which they weren’t) [1], at best the study could possibly suggest that mercury doesn’t cause autism. The problem with this is, there are so many ingredients in vaccines. Not just mercury. This is the epitome of junk science. It doesn’t prove that aluminum or aborted fetal cells or formaldehyde or ether or antibiotics or bacteria, to name a few, couldn’t cause autism. And it doesn’t prove that an interaction between the many ingredients in a vaccine or between different vaccines given at the same time couldn’t cause autism.

To me, this would be like taking one ingredient out of cigarettes, seeing no drop in the cancer rate, and saying that cigarettes don’t cause cancer. What is the difference? There is no reasonable, logical thinking here, let alone scientific proof.


So, just briefly, I’ll stop thinking out loud and mention some of the quotes I’ve found on causation and correlation. I chose these because I think they are—you got it—reasonable and logical.

“Obviously, it is much more difficult to prove causation than it is to prove an association. Should we just ignore associations? No! Not at all!!! Not even close!!! Correlations are crucial for research and still need to be looked at and studied …” [2]

“It’s hard to nail down causation conclusively, as evidenced by tobacco company lawyers who argued for forty years that smoking merely ‘correlated’ to lung cancer rather than actually caused it. However, the least you can do is pause and ask yourself what other possible causes exist … If they do exist, you need to think through the evidence and determine why these other causes are less likely than the one you propose.” [3]

I think this is especially relevant to my grandson’s story (Unlocking Jake: The Story of a Rabies Vaccine, Recovery & Autism). Jake was 3½ years old when he developed autism after a series of rabies vaccines. As I’ve explained before, he was not sick, he was not on any medication, he hadn’t been bitten or stung by anything, and he hadn’t ingested any type of poison. Nothing could explain what happened to him except for the rabies vaccines. In my AutismOne interview on Voice America this week, Teri Arranga asked me if I thought the rabies vaccine could have been Jake’s toxic tipping point. I have thought about this a lot, and I’ll probably never know for sure. It’s possible. Maybe if he hadn’t had 30 doses of vaccines between 1 day old and 15 months old, he wouldn’t have regressed into autism after the rabies vaccines. The one thing I do know is that the rabies vaccine caused autism in my grandson. There was no other possible cause. None.

“…correlation does not imply causation, even though in fact some of the most important scientific advances have come precisely because scientists did investigate that implication. … Correlation is not causation but it sure is a hint.” [4] These are the words of Edward Tufte, Professor Emeritus of political science, statistics, and computer science at Yale University. Tufte holds a Ph.D in political science from Yale and a B.S. and an M.S. in statistics from Stanford University. In early 2010, he was appointed by President Obama to serve on the independent panel that advises the Recovery Accountability and Transparency Board. [5]

And, last but not least, from Austin Bradford Hill: “Finally, in passing from association to causation I believe in ‘real life’ we shall have to consider what flows from that decision. On scientific grounds we should do no such thing. The evidence is there to be judged on its merits and the judgment (in that sense) should be utterly independent of what hangs upon it—or who hangs because of it. But in another and more practical sense we may surely ask what is involved in our decision.” [6] It’s pretty obvious who stands to lose when the truth about vaccines and autism can no longer be denied.

Hill (1897–1991), by the way, was a British medical statistician who outlined criteria necessary to prove causation. “Hill’s Criteria” forms the basis of modern epidemiological research. You can read all nine of them, but one idea in particular stands out. Just because a perceived association (in this case, between vaccines and autism) doesn’t agree with established theory (that vaccines don’t cause autism), that doesn’t mean the association is false. “… It may, in fact, force a reconsideration of accepted beliefs and principles.” [7]




1. www.ageofautism.com/2012/04/revisiting-denmark-more-rotten-than-ever.html

2. www.psychologytoday.com/blog/all-about-addiction/201003/correlation-causation-and-association-what-does-it-all-mean.

3. http://web.cn.edu/kwheeler/logic_causation.html

4. www.psy.gla.ac.uk/~steve/best/correlation.html

5. www.businessweek.com/innovate/NussbaumOnDesign/archives/2010/03/president_obama_8.html

6. www.edwardtufte.com/tufte/hill

7. www.drabruzzi.com/hills_criteria_of_causation.htm


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Jennifer Hutchinson

Jennifer Hutchinson is a freelance editor and writer. She has devoted the last few years to helping Jake recover, researching autism and vaccines, and sharing what she knows with others. She lives in Winchester, Virginia, with Ann and Jake.