This is about antivaccine happenings ten years’ time ago. Unfortunately, it’s also about antivaccine happenings now. The reason, and what links the two, is that antivaccine happenings, particularly myths, never seem to die. They just keep coming back over and over again. One myth that’s been recycled since at least 2005 is the one that claims that there’s been a study that has vindicated Andrew Wakefield. Stories pop up every so often that look for all the world as though they’re new claiming that the results of Andrew Wakefield’s original Lancet case series has been replicated. Sadly for Wakefield (and happily for the rest of the world), it’s just not true. I have a Google Alert for vaccines set up, so I see these stories when they pop up periodically. Sometimes they even make an appearance on Facebook and/or Twitter as antivaccine memes.

This time around, what’s happening is not exactly the same thing. The “Wakefield was right” news stories appear to arise organically every so often. I have no idea why. This particular story is one that’s being desperately pushed by antivaccine mavens—again. It’s one that has been desperately promoted dating back to a decade ago, as you will see. Unfortunately, like Jason or Michael Myers in a classic slasher flick, just when you think it’s dead is the time to be vigilant because it’s not. I’m referring to a myth that I’ve been covering on and off for nearly a decade that the Centers for Disease Control (the CDC) has been “hiding evidence” that mercury in vaccines is a major cause of the “autism epidemic.” It’s not true, of course. Indeed, my very first post for this blog lo these six years ago referred to the hypothesis that mercury in the thimerosal preservative that used to be used in childhood vaccines as a failed hypothesis. And so it is—and remains.

None of that prevents a very vocal bunch of cranks from trying very hard to exhume the rotting corpse of the hypothesis, hook it up to steampunk-appearing equipment straight out of a Frankenstein movie and fire thousands of volts of electricity through it to reanimate it. This time around, it’s Brian Hooker, PhD, whom we’ve only met very briefly before on this blog. However, those of you who follow certain other blogs (such as my not-so-secret other blog) have met Dr. Hooker, a biochemist who fancies himself a vaccine expert. He’s also known for having presented at the yearly AutismOne quackfest, along with Tim Bolen, clearly one of the crankiest cranks in existence, as anyone who’s been following issues of antivaccine beliefs and quackery is likely to know.

I must admit that, until now, I had been assiduously avoiding this particular topic. I must confess that the reason was because I was so incredibly tired of this particular line of “reasoning,” such as it is, having first dealt with it nine years ago. Unfortunately (for me, not for you I hope) no one at SBM had taken on this particular claim before, which means that I feel as though I have to. I realize that this is a bit repetitive for people who follow me both here and at my not-so-secret other blog, but I thought the issue important enough to risk more repetition than usual. Let’s just put it this way. I hope that I can write this and that you can just post it in response whenever you see this particular claim/meme pop up on Facebook or wherever. I can only hope that it will suffice for a reasonable period of time in the future, so that I don’t have to revisit this topic again any time soon.

So let’s go back a bit. This particular claim – that the CDC has been “hiding” or “covering up” evidence that in reality the mercury in thimerosal in vaccines really has been causing autism all along – has been all over, in press releases, on SafeMinds, on the “boy wonder” Jake Crosby’s blog, and, of course, on the antivaccine crank blog Age of Autism. The origin of this claim appears to be a document obtained by Brian Hooker, whose “mistreatment” at the hands of SafeMinds and the antivaccine luminaries at AoA led to his becoming the Frankenstein’s monster they could no longer control. I’m referring, of course, to the Brian Hooker whose epic fails when it comes to vaccine science go beyond epic.

Let’s go to the press release, straight from Hooker himself:

Dr. Hooker, a PhD scientist, worked with two members of Congress to craft the letter to the CDC that recently resulted in his obtaining long-awaited data from the CDC, the significance of which is historic. According to Hooker, the data on over 400,000 infants born between 1991 and 1997, which was analyzed by CDC epidemiologist Thomas Verstraeten, MD, “proves unequivocally that in 2000, CDC officials were informed internally of the very high risk of autism, non-organic sleep disorder and speech disorder associated with Thimerosal exposure.”

When the results of the Verstraeten study were first reported outside the CDC in 2005, there was no evidence that anyone but Dr. Verstraeten within the CDC had known of the very high 7.6-fold elevated relative risk of autism from exposure to Thimerosal during infancy. But now, clear evidence exists. A newly-acquired abstract from 1999 titled, “Increased risk of developmental neurologic impairment after high exposure to Thimerosal containing vaccine in first month of life” required the approval of top CDC officials prior to its presentation at the Epidemic Intelligence Service (EIS) conference. Thimerosal, which is 50% mercury by weight, was used in most childhood vaccines and in the RhoGAM® shot for pregnant women prior to the early 2000s.

My first reaction to this claim was a massive, massive yawn. Why is that? Quite simply, I thought I was having an acid flashback to 2005, as this bogus argument dates back at least that far. For example, see this post. It’s not about the Verstraeten study specifically per se, although it does mention it as an example of how successive iterations of data analysis can result in an effect size seen in preliminary analyses shrinking away to nothing as successive, more rigorous analyses are performed. It’s a common thing in science, particularly clinical science. Physicians know it and expect it. We’re not surprised by it. Indeed, we have an instinctive tendency to be skeptical of large effects reported in early studies because we know they often dissipate in later studies and analyses. There’s even a term that’s been coined for one type of this observation, the “decline effect.”

Hooker, determinedly oblivious to such considerations, along with the antivaccinationists who have been hatching all manner of conspiracy theories about the Verstraeten study for the last decade, do not know it and do not expect this natural and common phenomenon in science. So when they see it, their natural inclination is to assume that it must be a conspiracy.

Hence the yawn.

Indeed, my yawn was so intense that when a reader wrote asking me to take this on or point her to a debunking of this particular bit of antivaccine nonsense, I demurred at first. Basically, I said that the whole matter bored me and that if I were to write about the Verstraeten study again it would be far more out of a sense of duty than out of any real interest. After all, I never thought that, nearly nine years after this particular conspiracy theory appeared, thanks to everybody’s favorite antivaccine crank, Robert F. Kennedy, Jr., the same misinformation would be reappearing, like some crazed Whac-A-Mole™ that needs to be slapped down yet again. Key to RFK Jr.’s conspiracy theory is the claim that somehow, at a meeting in suburban Atlanta at a conference center known as Simpsonwood, the CDC somehow cooked the numbers to “cover up” evidence that, contrary to CDC assurances, thimerosal in vaccine really was strongly associated with autism. Of course, as explained by Skeptico and myself, RFK, Jr.’s account of what happened at Simpsonwood was shockingly dishonest, as anyone can see for himself if he takes the time to read the entire 286 page transcript.

So what’s got Hooker and his antivaccine buddies’ knickers in a knot? To understand this, you need to understand a couple of things. First, the Simpsonwood conference was all about examining evidence from the Vaccine Safety Datalink (VSD), a collaborative effort between the CDC’s Immunization Safety Office and nine managed care organizations (MCOs) established in 1990 to monitor immunization safety and address the gaps in scientific knowledge about rare and serious events following immunization to determine if there really was a reason for concern about thimerosal in vaccines. Although the decision had been made in 1999 to remove thimoerosal from childhood vaccines, the decision hadn’t been fully implemented yet, and the CDC wanted to determine whether there was any cause for concern. It was hardly the action of a group that wanted to “cover up” anything, particularly the bit about publishing the entire transcript. None of this, however, prevented antivaccine activists, particularly the branch known as the “mercury militia” for its affinity for the set of antivaccine beliefs associated with mercury in vaccines as a cause of autism, from dreaming up all manner of conspiracy theories, with the CDC meeting in a “secret” location to cackle over the “autism epidemic,” rubbing their hands together gleefully as they plotted to create a generation of autistic children. (I exaggerate, but really only slightly.) Of course, it didn’t help that Verstraeten ultimately left the CDC and went to work for pharma, which only fueled the hype.

Various antivaccine groups, from SafeMinds on, have been filing Freedom of Information Act (FOIA) requests for well over a decade. Apparently one of Hooker’s numerous frivolous requests finally panned out. Or so he thinks. What he described above in the press release is an abstract presented by four authors, including Verstraeten, at the CDC’s yearly conference in 1999 for the fellows of its Epidemic Intelligence Service. It was a preliminary study, as such abstracts often report, and it reported a relative risk for developing a neurological developmental disorder, comparing the group with the highest exposure to thimerosal at one month compared to no exposure, of 1.8 (95% confidence interval 1.1 to 2.8). In other words, there was a statistically significant difference, but the error bars almost encompassed one. You can get an idea of how preliminary the report is by looking at the 95% confidence intervals for some of the relative risks for some of the conditions reported: autism (RR 7.6, CI=1.8 to 31.5) and sleep disorders (RR 5.0, CI=1.6 to 15.9). These are the preliminary data in which the RR was reported to be 7.6, the original abstract that was said to be “watered down” to a less worrisome abstract to be presented at Simpsonwood. Sounds damning, right?


The Verstraeten VSD study was always intended to be a two phase study, as Emily Willingham and Lindsay Beyerstein reported. They both explain it well, but I think I’ll go to the source, Verstraeten himself, who wrote a letter to the editor of Pediatrics in 2004 about the study:

Did the CDC water down the original results? It did not. This misconception comes from an erroneous perception of this screening study and other epidemiological studies. The perception is that an epidemiological study can have only 1 of 2 outcomes: either an association is found (or confirmed), or an association is refuted. Very often, however, there is a third interpretation: an association can neither be found nor refuted. Let’s call the first 2 outcomes “positive” and “negative” and the third outcome “neutral.” The CDC screening study of thimerosal-containing vaccines was perceived at first as a positive study that found an association between thimerosal and some neurodevelopmental outcomes. This was the perception both independent scientists and antivaccine lobbyists had at the conclusion of the first phase of the study. It was foreseen from the very start that any positive outcome would lead to a second phase. Whereas the original plan was to conduct the second phase as a case-control study, we soon realized this would be too time consuming. The validity of the first-phase results needed urgent validation in view of the large potential public health impact. Did the CDC purposefully select a second phase that would contradict the first phase? Certainly not. The push to urgently perform the second phase at health maintenance organization C came entirely from myself, because I felt that the first-phase results were too prone to potential biases to be the basis for important public health decisions. Health maintenance organization C was the only site known to myself and my coauthors that could rapidly provide sufficient data that would enable a check of the major findings of the first phase in a timely manner.

Because the findings of the first phase were not replicated in the second phase, the perception of the study changed from a positive to a neutral study. Surprisingly, however, the study is being interpreted now as negative by many, including the antivaccine lobbyists. The article does not state that we found evidence against an association, as a negative study would. It does state, on the contrary, that additional study is recommended, which is the conclusion to which a neutral study must come.

In other words, the first part of the study was the screen, to see if there might have been an effect, in which the study was designed to look for associations that, by the design of the study, would need to be, if found, confirmed in the second phase of the study. In this case, it wasn’t. As I said before, this is not an uncommon thing to happen with studies in medicine. Frequently early phases of studies are positive, because they’re designed to look for associations with high sensitivity but with a tendency for a high rate of false positives. Scientists want to see if something might be there. Then they need to test if any associations they find in a first pass-through hold up to scrutiny. In this case the association between vaccines and autism didn’t, and, because of the design of the study, this meant that the study could neither confirm nor entirely refute an association between thimerosal and autism. The conspiracy-mongering RFK, Jr. made it sound as though phase II of the study was tacked on specifically to try to discredit the findings of phase I, but nothing could be further from the truth. Phase II was “baked in,” included in the original design. The only controversial feature was to use an HMO in Massachusetts to crosscheck phase I results, and this was done out of a sense of urgency to get results, not for any nefarious purposes. This happens sometimes; practicality and external exigencies can result in such decisions on the parts of investigators. There was no cover-up, no attempt to whitewash an association.

Of course, no antivaccinationist is ever going to believe that because the source is Verstraeten and because they don’t understand how often studies in medicine start out promisingly positive, only to have associations disappear as more and more confounders are controlled for and more and more rigorous analyses are done.

None of this stops Jake Crosby from attacking Emily Willingham’s analysis in a fashion that really makes me wonder how on earth he graduated from an MPH program, given how lacking in scientific and epidemiologic understanding it is. He engages in the same sort of conspiracy-mongering that Hooker does, only using an e-mail from Verstraeten in which he does what scientists frequently do: Explores different analyses of the data. It even refers to the abstract he had presented.

Of course, since the Verstraeten study, we have multiple other high quality studies that have failed to find a whiff of a hint of an association between thimerosal-containing vaccines and autism. So even if everything Hooker and Crosby says about the Verstraeten study were true, and the CDC did “cover up” a positive study, it wouldn’t matter because it would be an outlier. The fall of the hypothesis that mercury in vaccines causes autism does not depend on the Verstraeten study. It never did. If it were truly positive for an association between thimerosal-containing vaccines and autism, more study would have needed to be done. If it were correctly interpreted as “neutral,” as Verstraeten puts it, more study would have needed to be done. More study was done and it was negative. The antivaccine movement’s obsessive focus on the Verstraeten study is nothing more than a conspiracy theory, and not a very convincing one at that—except, of course, to the antivaccine movement.

In fact, as I’ve known for years and as Emily Willingham summarizes, none of this is even new information! Seriously. It’s not. Look at slide #41 in this PowerPoint presentation by David Kirby, who in 2004 made his name in antivaccine circles by publishing a book, Evidence of Harm, which claimed that mercury in vaccines was the cause of the “autism epidemic. Actually, never mind. I’ll show you the slide:


Notice that it says it was an FOIA (that’s Freedom of Information Act) request that provided the Verstraeten data that reported a relative risk for autism of 7.6 in children exposed to thimerosal-containing vaccines. Everything old is new again.

And again.

And again and again and again and again.

This particular meme isn’t new in 2014. It wasn’t new in 2005. It wasn’t new even a decade ago.

Same as it ever was.

Posted by David Gorski

Dr. Gorski's full information can be found here, along with information for patients. David H. Gorski, MD, PhD, FACS is a surgical oncologist at the Barbara Ann Karmanos Cancer Institute specializing in breast cancer surgery, where he also serves as the American College of Surgeons Committee on Cancer Liaison Physician as well as an Associate Professor of Surgery and member of the faculty of the Graduate Program in Cancer Biology at Wayne State University. If you are a potential patient and found this page through a Google search, please check out Dr. Gorski's biographical information, disclaimers regarding his writings, and notice to patients here.