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Another very bad day for antivaccinationists: Yet another study fails to find a link between thimerosal and autism

Blogging on Peer-Reviewed ResearchA little more than three months ago there came to pass a very bad day for antivaccinationists.

On that day, in the prestigious New England Journal of Medicine appeared a study that was powerful evidence that vaccines are not associated with adverse neuropsychiatric outcomes in children. Not surprisingly, the usual suspects in the mercury militia went on the attack immediately, not wanting to believe that yet another strong piece of evidence was attacking their hallowed belief that mercury in the thimerosal preservative previously used in vaccines is a major cause or contributer to the development of autism.

Yesterday was another very bad day for antivaccinationists, a very, very bad day indeed. Three months ago, the study released that supported the safety of vaccines did not directly deal with autism and autism spectrum disorders. Yesterday, however, a study was released in the Archives of General Psychiatry that did study the question of whether vaccination with thimerosal-containing vaccines is at all correlated with the development of autism or autism spectrum disorders. Not surprisingly, given the growing number of other studies that have failed to find an association, the answer was a resounding “No!”

Regarding the question of vaccines and autism, we can’t do a double-blind, randomized, control trial of vaccines with and without thimerosal in the face of a pre-existing vaccination program. It wouldn’t be ethical. However, we can do the next best thing, and, indeed, we now have several good studies since 1999 that did just that in other countries that removed thimerosal from their vaccines before the U.S. did. Some of these studies are epidemiological; some are ecological. What allows us to use them to reject the hypothesis that mercury in vaccines is an etiological agent that is either associated with or causes autism is a very simple but powerful prediction that thimerosal hypothesis makes. Quite simply, if the hypothesis is true and thimerosal-containing vaccines (TCVs) cause autism (or are a significant contributing factor), we would expect that the removal of thimerosal from vaccines should lead to a rapid decrease in autism prevalence within 3-5 years.

It really is just that simple. What isn’t so simple is to design a study to ask this question that is sufficiently free of confounding factors to prevent a false positive or false negative result. We are now nearly six years out from the near-complete removal of thimerosal from vaccines. Other than the flu vaccine, there is no more than trace thimerosal in childhood vaccines; overall mercury exposure due to vaccines has not been as low as it is now in decades. Consequently this hypothesis can now be tested in the United States.

In a beautifully ironic twist that makes me smile just thinking about it, Schechter and Grether chose to use a source of data that has frequently been widely abused by advocates claiming a link between TCVs and autism to try to show one where there isn’t one as though the conclusions were foreordained. Although it is not, it has even been referred to as the “gold standard” of autism epidemiology by none other than David Kirby. Indeed, this is the very same database in which David Kirby predicted that there should be a noticeable decrease in new diagnoses of autism by 2007 if the thimerosal hypothesis is true and then later shifted the goalposts to 2011 when it became apparent that there has been no decrease. This source is the California Department of Developmental Services (CDDS) database. The CDDS administers a statewide system of regional centers and developmental centers designed to serve people who are substantially disabled because of autism, mental retardation, or other developmental disabilities. It maintains an archive file of client developmental evaluation reports on clients enrolled in the system. Of course, what’s particularly amusing is how the mercury militia members who once touted the CDDS database as the be-all and end-all of autism epidemiology have, now that it is not showing what they want it to show, suddenly found religion about its shortcomings and the difficulties inherent in deriving autism prevalence rates from it. Among the strengths of the system are that it is a population-based system representing the most populous state in the U.S. Moreover, the client reporting form was consistent throughout the study period, preventing confounders due to changes in reporting. The weaknesses of the CDDS is that its data is derived from an administrative system that was designed to track enrollment and fiscal data and is not as well suited to measuring the occurrence of developmental disabilities in the population. However, with proper statistical analysis, considerable information can still be gleaned from this data for specific birth cohorts.

In order to ask the question of whether autism rates had declined, Schechter and Grether examined data for clients with active status reported from January 1, 1995 to March 31, 2007. Using careful statistical analyses, they used two approaches to measure the occurrence of ASD during this period. The second approach, in which ASD prevalence was determined in the 3 to 5 year old cohort, is perhaps the most informative. It shows a continuing increase in autism prevalence without even a blip or decrease in the rate of increase after 2002. Indeed, showing the skill of some bloggers to analyze the same data, the money figure in the paper (Figure 3) looks almost exactly the same as the graph prepared in early 2007, a continually increasing curve since 1995. This result is not only consistent with multiple other published and unpublished studies, including the famous (or, if you’re an antivaccinationist, infamous) Danish and Canadian studies, but it is about as unambiguous evidence as can be obtained from a database like the CDDS database. Indeed, despite the known limitations of the use of this database, it is an excellent example of proponents of a “mercury injury” hypothesis of autism being “hoisted by their own petard,” so to speak.

In a pointed editorial that accompanied the study, Eric Fombonne asked the same question that I’ve been asking for the last two years now about the magical thinking that leads the mercury militia to cling to this failed hypothesis no matter how many studies fail to support it:

Despite the accumulation of scientific evidence rejecting these 2 hypotheses linking autism to various components of childhood vaccines, these theories and the practices that accompany them have not faded away. Why? How many more negative study results are required for the belief to go away, and how much more spending of public funds on this issue could even be justified

This is an excellent question. Millions of dollars of taxpayer money are likely to be spent studying this hypothesis, virtually all thanks to the political clout of activists and antivaccinationists legislators like Indiana’s Dan Burton. Moreover, the hypothesis that mercury in vaccines was the cause of an “autism epidemic” was never particularly scientifically plausible in the first place; it was just barely plausible enough that activists with an agenda could make scientists throw up their hands and say, “All right, let’s take a look.” Powerful forces are at work to keep this hypothesis on life support, to the point where the federal government has even invited known antivaccinationists to sit on the new Interagency Autism Coordinating Committee. It doesn’t matter that, in the face of the onslaught of multiple new studies like this that fail to find even a whiff of a correlation between TCVs and autism, even some of the most diehard zealots are starting to back away from the attitude of “it’s the mercury in vaccines, stupid.” In the meantime, even David Kirby and those more zealous than him were starting to back away from the hypothesis, invoking hand-waving and vague “environmental toxins” or even going so far as to blame mercury from pollution wafting over from China or, even more ludicrously, mercury from the cremation of bodies with mercury amalgam dental fillings.

So what’s an antivaccinationist to do when faced with yet another study that does not support his hypothesis? Well, if you’re Mark Blaxill, one of the commandants of the mercury militia, you could start weaseling away:

Put another way, the epidemiological analysis doesn’t prove that thimerosal exposure cannot cause individual cases of autism. It simply provides evidence that it’s unlikely thimerosal can be the sole cause in all cases.

This is true as far as it goes, but deceiving. Remember, the message two years ago was that autism and ASDs are all “misdiagnoses for mercury poisoning.” That was the claim, not that maybe, just maybe, thimerosal could cause autism in some children. Come on, Mark, what happened to all those pictures of autistic children with skulls and crossbones nearby and the words “mercury-poisoned” underneath? What happened slogans like “AUTISM: It’s the mercury, stupid“? What happened to the comparisons of the “autism epidemic” to the Holocaust?

If you’re Mark Blaxill, you could also stick your fingers in your ear and shout, “Nah, nah, nah! I can’t hear you!” while claiming that the scientific evidence still supports the plausibility of a link between thimerosal and autism:

The evidence regarding the connection with autism and mercury exposure more generally hasn’t changed. The plausible theories regarding the biology of excretion and toxicity of mercury compounds and their different effects on the developing immune system, gastrointestinal system and brain haven’t been affected a single bit.

Except that these hypotheses (they’re not theories, Mark; theories must pass a much higher standard of evidence) are not plausible and are based on dubious scientific studies. Even if they were somewhat plausible, the epidemiological studies are not supporting them. When that happens, real scientists abandon such hypotheses.

Other possible approaches for antivaccinationists present themselves. For example, if you’re Wendy Fournier and Rita Shreffler of the National Autism Association, you can put out press releases repeating the same fallacy of correlation equally causation coupled with canards about biomedical interventions:

  • Why do so many children regress into autism after receiving vaccines, subsequently have symptoms of heavy metal toxicity, then get better when mercury is removed through chelation?
  • How can mercury and other toxic metals be removed from the bodies of our children more safely and efficiently?
  • What biological abnormalities exist that cause some individuals to be unable to detoxify heavy metals?

The answer to question #1 is because the ages at which the symptoms of autism often first manifest themselves overlaps the ages at which children are getting most of their vaccinations. Moreover, there is no evidence that “heavy metal poisoning” causes autism or that chelation therapy cures it; so asking how mercury and “other toxic metals can be removed from the bodies of our children” is not the right question.

Of course, if there’s one thing, though that I predicted a long time ago, it’s that, should the evidence finally start forcing the mercury militia to face the reality that thimerosal does not cause autism, they would show their true antivaccinationist colors, because it’s really not about the mercury. It’s about vaccines in general. If the weight of scientific evidence becomes so crushingly overwhelming that even Ferrous Cranus reluctantly, slowly, and painfully must yield, they’ll start blaming other “toxins” in vaccines or vaccination in general for autism. And, indeed, that’s just what these antivaccinationists do.

Quoth Mark Blaxill:

Most importantly, and this is a point that escapes Fombonne’s Lilliputian mind entirely, the evidence from the California natural experiment doesn’t exonerate the broader childhood immunization program. Quite the opposite, it brings the overall escalation in the vaccine program even more strongly under suspicion. While thimerosal was removed from hepatitis B, Hib and DPT/DTaP vaccines (but not from influenza vaccines), the vaccines themselves didn’t go away. Indeed the total count of vaccine doses has gone from 15 to 45 by the first grade and this increased exposure is strongly associated with the increases in autism rates.

Never mind that non-thimerosal-containing vaccines are not associated with autism either.

Quoth Wendy Fournier:

NAA also cited confounding factors associated with the study, which includedthe failure to address synergistic effects of mercury, aluminum and other toxic ingredients. “Thimerosal isn’t completely gone from vaccines. It is still present in trace amounts. Since no safe level of neurotoxins such as mercury and aluminum have been established, trace amounts cannot be cleared of having caused injury, especially in susceptible children,” according to NAA board member Scott Bono.

Except that thimerosal exposure from vaccines is lower now than it has been in decades. If thimerosal is such a strong cause of autism that even trace amounts can cause as much autism and ASDs as we see today, then there should have been as many cases noted in the 1980s. There weren’t.

Most telling are two statements. The first is by über-antivaccinationist Barbara Loe Fisher, who, while claiming that the rates of increase of new cases is leveling off (which, even if true, is (1) moving the goalposts post hoc, given that the prediction was the autism prevalence would rapidly fall once thimerosal was removed from vaccines, and (2) to be expected if, in the face of expanded awareness and the broadening of diagnostic criteria for autism and ASDs, autism prevalence under the new criteria was finally approaching the true prevalance rate):

During the past quarter century, the CDC and AAP increased the numbers of vaccinations doctors are told to give American children from 23 doses of 7 vaccines to 48 doses of 14 vaccnies by age five. Although today almost all childhood vaccines contain only trace amounts of mercury or never contained mercury preservatives, such as polio, pneumococcal, hepatitis A and live virus MMR, chicken pox and rotavirus vaccines, parents around the nation continue to report that their children are regressing physically, mentally and emotionally following receipt of multiple vaccines. These parents report their children are becoming chronically ill and disabled, suffering with autism, learning disabilities, ADHD, asthma, diabetes, intestinal bowel disorders and other brain and immune system dysfunction.

How many more children will be hurt before government, industry and pediatricians open their eyes and see what too much vaccination has done to our children?

Once again: Neither the MMR nor other non-thimerosal-containing vaccines are associated with autism, either. Not that facts or reality have any effect on Fisher’s irrational belief that vaccines are dangerous.

Rick Rollens, co-founder U. C. Davis M.I.N.D. Institute (as he loves to point out), in an e-mail sent to several autism activists (and that was forwarded to me) is even more blunt:

If by 2009-2010 there has not been ANY change in the rate of increase of new cases of autism entering California’s developmental services system, then we can scratch mercury in vaccines off our list of agents contained in vaccines as a cause, and; then begin concentrating on the numerous other poisons and toxic agents in vaccines such as aluminum, formaldehyde, MSG, live viruses, etc., and most importantly, the interaction of these and other toxic agents contained in the 34 doses of vaccines children receive from birth to two years old today.

Amazingly, elsewhere, he even parrots the “hidden hordes” canard, which has been debunked many times before. Rollen’s handwaving is nothing more than moving the goalposts once again and failing to recognize that the claim that mercury in vaccines causes autism is a failed hypothesis. Not that that stops zealots like Rollens. His attitude is particularly telling, especially his blatant statement that, if mercury is finally cleared, then it must be some other “toxin” in vaccines. It’s an attitude identical to the one that I pointed out two years ago and then made fun of a mere month and a half ago. Rollens’ statment shows that, for the antivaccinationists of the mercury militia, it really, truly isn’t about the mercury, their claims that they are not “antivaccine” notwithstanding. Always remember, for them, it is about vaccines themselves. If mercury in vaccines is exonerated as the cause of autism, they’ll blame the aluminum adjuvant. If aluminum is exonerated, they’ll blame the traces of formaldehyde. If the traces of formaldehyde are exonerated, they’ll either make the almost impossible to test claim that it is the “synergistic” interactions between multiple “toxins” in vaccines, or they’ll blame the one thing that can’t be removed from vaccines, the fragments of killed virus or bacteria used to provoke the specific immune response to the disease for which a vaccine is designed. The only thing they won’t blame is the water in vaccines, and even then, I’m not so sure about that. After all, it is dihydromonoxide.

By Orac

Orac is the nom de blog of a humble surgeon/scientist who has an ego just big enough to delude himself that someone, somewhere might actually give a rodent's posterior about his copious verbal meanderings, but just barely small enough to admit to himself that few probably will. That surgeon is otherwise known as David Gorski.

That this particular surgeon has chosen his nom de blog based on a rather cranky and arrogant computer shaped like a clear box of blinking lights that he originally encountered when he became a fan of a 35 year old British SF television show whose special effects were renowned for their BBC/Doctor Who-style low budget look, but whose stories nonetheless resulted in some of the best, most innovative science fiction ever televised, should tell you nearly all that you need to know about Orac. (That, and the length of the preceding sentence.)

DISCLAIMER:: The various written meanderings here are the opinions of Orac and Orac alone, written on his own time. They should never be construed as representing the opinions of any other person or entity, especially Orac's cancer center, department of surgery, medical school, or university. Also note that Orac is nonpartisan; he is more than willing to criticize the statements of anyone, regardless of of political leanings, if that anyone advocates pseudoscience or quackery. Finally, medical commentary is not to be construed in any way as medical advice.

To contact Orac: [email protected]

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