Not a CDC Coverup…A Case of Using the Wrong Analytical Method

Sometimes, you can get the job done even when you use the wrong tool.  However, sometimes the wrong tool produces the wrong results.

Sometimes, you can get the job done even when you use the wrong tool. However, sometimes the wrong tool produces the wrong results.

The “news story” headline is astounding: “Fraud at the CDC uncovered, 340% risk of autism hidden from public.” The article says that data in a 2004 CDC study on the relationship between the Measles, Mumps, and Rubella (MMR) vaccine and autism were purposefully hidden so it could deny a relationship between the two. Those hidden data supposedly show that some who got the MMR vaccine were significantly more likely to become autistic than those who didn’t. According to the article, this shows that the original study is “fraudulent,” and there is now a petition to get the study retracted. It also calls into question the other studies that the CDC often cites to show that there is no relationship between vaccination and autism. And this article has to be reliable. After all, it is on CNN’s website, right?

Well, not exactly. If you go to the article, you will see “NOT VERIFIED BY CNN” at the top, and you will find a CNN producer note that this website is the network’s “user-generated news community.” So the article wasn’t written by someone at CNN. It was written by a blogger. Does that mean it’s not reliable? Of course not. I read several blogs regularly, and I find most of the articles written on them to be very reliable. In fact, I would say that some blogs are more reliable than some standard media outlets! The question, of course, is whether or not this particular blog article is reliable. When you look into the details, you find that it’s not.

The article’s big claim is that by including data which were supposedly covered up by the CDC, you can find that African American boys have a 340% increased risk of autism if they got the MMR vaccine. This conclusion, however, was “hidden due to pressure from senior officials.” Of course, to make such a claim, someone must have done some sort of study. The article itself tells you nothing about that study, but the CNN Producer Note at the top indicates that it was a study done by Dr. Brian Hooker (a bioengineer) and was published in a journal called Translational Neurodegeneration. An update to that note indicates that the journal has pulled the study, and the journal says this is “because of serious concerns about the validity of its conclusions.”

That doesn’t sound very good, but then again, maybe the journal has been pressured by the CDC to participate in their elaborate coverup. Fortunately, I was able to read the study before it was pulled, and I have to agree with the journal’s decision. The study’s conclusions are obviously wrong, because it used the wrong kind of tool to evaluate the data.

Let’s start with the original study, which is supposedly now “fraudulent” because these new data were uncovered. It looked at 624 children with autism and matched them to 1,824 children who didn’t have autism. Right away, then, we see that this is a case-controlled study. Such studies are useful because there are probably a lot of factors that determine whether or not a child has autism. In order to compare autistic children with non-autistic children, then, researchers must try to compare “equivalent children.” A case-controlled study tries to do that, because it specifically looks for non-autistic children that have the same relevant characteristics as the autistic children being studied (school district, the age of the mother at birth, the kind of birth that was experienced, etc., etc.). Here is what they found:1

Similar proportions of case and control children were vaccinated by the recommended age or shortly after (ie, before 18 months) and before the age by which atypical development is usually recognized in children with autism (ie, 24 months). Vaccination before 36 months was more common among case children than control children, especially among children 3 to 5 years of age, likely reflecting immunization requirements for enrollment in early intervention programs.

So the percentage of children who got the MMR vaccine before the age when most autistic children show signs of autism was the same in both groups. This indicates the MMR vaccine has no effect on autism. However, the authors do note that if you expand the age of vaccination to 36 months, a slightly larger percentage of autistic children (93.4%) had gotten the MMR than non-autistic children (90.6%). Since this is past the age when most autistic children show signs of autism, the authors suggest that the small difference was probably related to the vaccination requirement for early intervention programs. Non-autistic children wouldn’t have a vaccination requirement until kindergarten, so the parents of the unvaccinated, non-autistic children wouldn’t be forced to deal with vaccination until then. If a parent had an unvaccinated autistic child and wanted early intervention, he or she would have to deal with the issue sooner.

What about the new study that supposedly includes the data that weren’t included in the original study? Why does it come to a different conclusion? Well, let’s first look at why these data weren’t included in the original study. They were from children who didn’t have a Georgia birth certificate! Remember, the original study was a case-controlled study. It needed to match autistic children to non-autistic children. One of the things you want to match is the conditions that occur at birth. If the child was born in another state, the conditions would likely be different. Thus, you don’t want those children in a study that is trying to match children as closely as possible! Rather than being the result of some sort of “coverup,” then, the data were excluded because they didn’t meet the criteria of the study. Another kind of study might have been able to use those data, but this kind of study could not.

That brings me to the second problem associated with this new study. The author used the wrong data analysis method. He treated the data like they were gathered for a cohort study and analyzed them that way. This doesn’t work. In a cohort study, you need large sample sizes. Since you aren’t trying to match autistic and non-autistic children, you need to hope that all the other factors that contribute to autism average out between the groups you are comparing. The only way to do that is to have a very large sample size. For example, a good cohort study on the MMR vaccine and autism was published in 2002.2 It studied 537,303 children. That’s a good sample size for a cohort study, and it found no relationship between the MMR vaccine and autism.

The number of children in this new study is great for a case-controlled study, but it is very poor for a cohort study. So using cohort study techniques on a case-controlled study is like using a knife as a screwdriver. You’re just using the wrong tool for the job. Of course, you don’t have to know this to see that there is a problem with the study. All you have to do is look at the conclusions. The author saw an increased risk of autism only for African American boys who received the MMR. He didn’t see an increased risk among the other groups that were analyzed. Why? Other studies show that the rate of autism diagnosis is the same among African Americans as whites, it just tends to occur later.3 How can something cause autism in African American boys and not in other children, despite the fact that the condition is roughly equivalent between the two groups?

The reason the new study sees the effect among African American boys is that they represent an even smaller sample. As a result, the analysis technique the author is using is even more unfit for this group. When you use the wrong tool for the job, you often end up with bad results. That’s what has happened here.

I am not surprised that Translational Neurodegeneration pulled the paper. I am surprised they published it in the first place.


1. Frank DeStefano, Tanya Karapurkar Bhasin, William W. Thompson, Marshalyn Yeargin-Allsopp, Coleen Boyle, “Age at First Measles-Mumps-Rubella Vaccination in Children With Autism and School-Matched Control Subjects: A Population-Based Study in Metropolitan Atlanta ,” Pediatrics 113(2):259 -266, 2004
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2. Madsen KM, Hviid A, Vestergaard M, Schendel D, Wohlfahrt J, Thorsen P, Olsen J, Melbye M, “A population-based study of measles, mumps, and rubella vaccination and autism,” New England Journal of Medicine 347(19):1477-82, 2002
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3. Gourdine RM, Baffour TD, and Teasley M, “Autism and the African American community,” Social Work in Public Health 26(4):454-70, 2011
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  1. Joel says:

    Dr. Wile, thanks for highlighting this study on your blog. I’m very much in agreement with your analysis here. I am aware of how difficult this topic can be given the emotional attachment many have to the subject. Your lesson on statistics is very important and a valuable contribution to the ongoing discussion about autism and vaccination.

  2. Stephanie says:

    What is so hard to understand about this whole thing is why a senior scientist such as Thompson would feel so strongly that the results of the “reanalysis” are not faulty. Unfortunately I’m not sure we’ll ever figure out why he felt the need to engage with Brian Hooker, at least not any time soon.

    1. jlwile says:

      I agree, Stephanie. I don’t know what Dr. Thompson’s training is. He might be a medical doctor. If that’s the case, he might not really understand the issues involved in the analysis. He might be a part of these studies simply because of his medical expertise. If he is trained in epidemiology or medical statistics, his behavior is truly baffling.

  3. Shawn Huston says:

    I wanted to chime in with agreement to Joel above. Thanks very much for tracking this down, Jay. I had seen the headline and had dismissed it but hadn’t followed through.

  4. Deanna says:

    While I appreciate the analysis, as a mom whose child lost all speech after a MMR vaccine at 22 months, I believe there is a connection between that particular vaccine and autism. I’ve seen it too many times among friends whose child had serious speech, intestinal, and exhibited signs of regression after the vaccine.

    I’m not a scientist but am highly educated. My son was 100 percent normal when we went for the appointment. Two days after his shot, he was unable to utter a word.

    Fortunately, after about six months, his speech began to reappear. He had to undergo testing for all types of intestinal disorders for a sudden appearance of bowel issues but that two eventually resolved itself. Although he is “normal” 13 year old now, he is very different personality wise from my other 8 children and has occasional problems interacting socially.

    Trying to reassure people there is no link because of an “unflawed” study does a disservice to the people who have seen first hand the dangers of certain vaccines. (By the way, I’m not anti-vac – but I am anti MMR.)

    1. jlwile says:

      Thanks for your comment, Deanna. I can see how such an experience can make you anti-MMR, but please understand that your experience (and the experiences of your acquaintances) doesn’t tell us anything about the MMR vaccine. An event occurring before a medical issue doesn’t tell us that the event caused the medical issue. For example, my brother-in-law works for a business that has semi-regular banquets. The day after one of those banquets, all the attendees were sick. Of course, the owner of the business thought that it was caused by the food at the banquet, so he called the caterer. The caterer was adamant that there was no food poisoning. The owner wanted to get to the bottom of this, so he sent some of his people to the doctor, who did blood tests. It turns out that the caterer was right. They all had the same virus. It was a virus that takes several weeks to incubate. They eventually figured out that all of them got it from a banquet six weeks earlier, where a visitor had spoken. He had the virus and gave it to the attendees then, and it took weeks for them to show symptoms. By sheer coincidence, the symptoms showed up the day after another banquet.

      This is why one must do studies to assess whether or not an event causes an illness, and the studies show no link between the MMR and autism.

      Please note that I am not trying to “reassure” people of anything, because I have no stake in whether or not people vaccinate. I am only trying to give people scientifically-correct information so they can make an informed decision on the issue.

  5. Cherie says:

    Thank you so much for a well thought out and clear explanation. Greatly appreciated!

  6. Kay Martin-Pence says:

    Very interesting Jay. I have always felt the original study was flawed…just a gut feel nothing scientific to back it up. Appreciate the analysis.

  7. David H says:

    I’m not usually this harsh, but the author of the CNN blog article to which you linked appears to be deliberately distorting the evidence.

    Here’s a very problematic paragraph in that blog article:

    “A recently released memo from 2004 of Dr. Thompson expressing concerns to Dr. Gerberding, the head of the CDC at the time, about this problematic study has citizens upset. Does this mean Dr. Gerberding could have committed perjury during a congressional hearing? More investigation will be needed to know. A copy of the letter obtained under FOIA can be found here.”

    What follows is a link to a picture file on the website. I presume the picture file is supposed to be a scanned paper letter. But the link is broken — if you click on it you’ll just get an error message in your browser.

    I noticed that the link URL appeared to be malformed — it ends with “.jpg g” (a space and then an additional “g”.) I deleted the extra “g” and the space, and then I was able to read the letter. Here is the corrected link:

    If you read this letter you’ll see it is not at all what was represented in the blog article. This letter is not “about this problematic study”. Instead, the letter is a request that Dr. Gerberding, apparently a leader at the CDC, respond to a politician’s inquiry so as to make the CDC appear more responsive to the public. His immediate reason for this request is that he (Dr. Thompson) is about to present a talk on immunization safety to a “hostile crowd of parents with autistic children who have been told not to trust the CDC”. He wants Dr. Gerberding to make a gesture of goodwill so that his task is not made any more uncomfortable than it already is. While the letter (meant to be strictly internal) is not flattering to the CDC in terms of its public relations skills, it is in no way any kind of indictment or revelation concerning a coverup. It doesn’t mention any flaws in any studies.

    In other words, the blog author appears to be distorting the facts and misrepresenting evidence. Which makes me not trust the article’s conclusions.

    I just wanted to pass this on because not everyone would notice that broken URL or know how to fix it, and therefore might have just ignored the error message and not seen the letter’s actual contents.

    1. jlwile says:

      Thanks for doing the digging on that, David H. You are right. It seems to be a direct distortion of the evidence.