Search Results for "thimerosal"

Aug 24 2015

Antivaxxers Still Flogging Thimerosal

I gave a talk on the vaccine controversy over the weekend. I was not surprised that a couple of audience members had a lot of questions taken directly from anti-vaccine propaganda sites. What was interesting was that they were still pushing the idea that thimerosal, a mercury-based vaccine preservative, is linked to autism.

The reason this is interesting and illuminating is that the thimerosal hypothesis is not just mostly dead, it is most sincerely dead. It is pushing up the proverbial daisies.

A Brief History of Thimerosal

Thimerosal was developed as an organomercurial anti-microbial agent shortly after World War I. It was soon discovered that it has great anti-microbial properties and was well tolerated when injected into rabbits or rats even at high doses. This made it superior to anything else available at the time.

Bacterial contamination was a serious problem for vaccines in the first half of the 20th century. Thimerosal in tiny doses, well below safety limits, proved to be an effective agent for preventing contamination. By the 1940s thimerosal was being added to several vaccines for this purpose.

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Sep 13 2010

The Long Awaited CDC Trial on Thimerosal and Autism

We can add one more study to the pile of evidence showing no association between exposure to thimerosal (a mercury-based vaccine preservative) and autism. The article: Prenatal and Infant Exposure to Thimerosal From Vaccines and Immunoglobulins and Risk of Autism, is published in the latest issue of Pediatrics, and shows no association between prenatal and infant exposure to thimerosal and three forms of autism – autism, autism spectrum disorder, and regressive autism.

No one study can ever be definitive, but now we have a large body of evidence from multiple studies showing a lack of association between thimerosal and autism. This won’t stop the dedicated anti-vaccinationists and mercury militia from continuing their anti-vaccine propaganda, but hopefully it will further reassure those who actually care about the science.


This has been a long and complex story, so let me review some of the background. Diagnosis rates of ASD have been climbing for the last 20 years, prompting some to search for an environmental cause. The existing anti-vaccine community, not surprisingly, blamed vaccines. This was given a tremendous boost by the now-discredited study by Andrew Wakefield concerning MMR (which never contained thimerosal) and autism. When the evidence was going against MMR as a cause, attention turned to thimerosal in some vaccines. This notion was popularized by journalist David Kirby in his book, Evidence of Harm.

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Jan 27 2009

Yet More Evidence Against a Link Between Thimerosal and Autism

Published by under Uncategorized

A new study published yesterday (Monday) in the journal Pediatrics provides more evidence against any link between thimerosal (a mercury-based preservative in some vaccines) and autism or other neurological disorders. This study adds to the large and growing body of scientific evidence for the safety of vaccines, and contradicting the claims of the anti-vaccine movement that vaccines cause autism.

The study is a bit fortuitous in that it was not originally designed to probe this question. Rather, this was a safety and efficacy study of the acellular pertussis vaccine conducted in Italy between 1992 and 1993. But it created a cohort of children who were carefully screened and monitored, and randomized to different exposures to thimerosal. This allowed the researchers to go back 10 years later to survey and examine the children for neurological disorders.

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Feb 17 2015

Anderson Cooper Takes Down Dan Burton

Published by under Skepticism

I criticize bad, biased, and or just lazy science journalism frequently, and so it’s a pleasure to occasionally have the opportunity to praise good journalism. This recent interview of Dan Burton by Anderson Cooper could be a template for how to conduct an interview over a scientific issue.

Dan Burton is a former Republican Congressman who has a long history of being anti-vaccine. He likes to repeat anti-vaccine tropes, and does so with the clueless persistence of a seasoned politician with an agenda.

Anderson Cooper is one of the few American journalists who has demonstrated his ability to do a tough and probing interview – you know, actual journalism. He demonstrated his chops again here. Specifically:

He was clearly prepped for the interview. He did his research, understood the issues, and was able to challenge Burton on specific points. You can’t go into an interview like this cold, or with only a superficial understanding of the issue. You have to know what the other person is going to say and how to respond.

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Sep 12 2014

Features of Denialism

Published by under Pseudoscience

Denialism is a thing. What I mean is that denialism is a definable intellectual strategy, with consistent features that tend to cluster together. I first wrote about denialism 12 years ago, before global warming denial made the term more widespread. I pointed out that certain beliefs tend to follow the same fallacious arguments – HIV denial, creationism (evolution denial), holocaust denial, and mental illness denial. I would add now global warming denial and germ theory/vaccine science denial.

I characterized denialism as a subset of pseudoscience, one that tries to cloak itself in the language of skepticism while eschewing the actual process of scientific skepticism. But further, denialism exists on a spectrum with skepticism, without a clear demarcation in between (similar to science and pseudoscience). People also tend to use themselves for calibration – anyone more skeptical than you is a denier, and anyone less skeptical than you is a true believer.

Geneticist Sean B. Carroll (not to be confused with the physicist Sean M. Carroll) in his 2007 book, The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution, lists what he identified as the six core features of denialism. I think they make an excellent list, and would like to expand on them:

1) Cast doubt on the science.
2) Question the scientists’ motives and integrity.
3) Magnify any disagreements among the scientists; cite gadflies as authorities.
4) Exaggerate the potential for harm from the science.
5) Appeal to the importance of personal freedom.
6) Object that acceptance of the science would repudiate some key philosophy.

As you will see, all of these strategies are insidious because they are extreme versions of reasonable positions. Their underlying principles are sound, it is their specific application that is the problem.

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Mar 27 2014

When Does Autism Begin?

One common feature of unscientific belief systems is that they do not change in the face of new evidence. They tend to evolve like cultural beliefs or marketing campaigns, but do not appear to be affected by scientific evidence in any meaningful way.

One great example of this is the idea the autism is linked to vaccines (to be clear up front, it isn’t) This idea had a few important factors in its origin. The first was simply the existing anti-vaccine movement searching for anything to blame on vaccines. The second, and perhaps decisive, factor was the now discredited and withdrawn study by Andrew Wakefield linking autism to the MMR vaccine.

Even as the MMR claim was dying, the anti-vaccine community was moving onto the next target – mercury (specifically the preservative Thimerosal). This was the target of the book Evidence of Harm by David Kirby. This also created common cause between the anti-vaccine movement, and separate “mercury militia” blaming many modern ills on mercury, and some environmentalists (most prominently Robert Kennedy Jr.) who are keen to blame medical problems on any environmental exposure, including mercury and/or vaccines.

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Jul 29 2013

Legal Courts And Science

Facebook is like a graveyard in a zombie movie, where old news items rise from the dead to have a second life. I am often asked about news items that are burning up Facebook, only to find that they are years old, but never-the-less they have to be addressed all over again. ]

One such item (actually a few items) is a 2012 news report about the Italian courts awarding money to the Bocca family a large reward because it concluded their 9-year-old son acquired autism from the MMR vaccine.

History here is a useful guide. The courts have historically often been out-of-step with the science, tending to err on the side of awarding compensation for possible harm. For example, until about the 1920s it was thought that physical trauma could cause cancer. Animal studies and epidemiological evidence, however, showed that there was no causal connection. Recall bias and increased surveillance were likely the cause of the apparent association.

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Apr 04 2013

Vaccines are Gay

It’s always amusing to see two pseudosciences combined into one greater pseudoscience – it’s like chocolate and peanut butter. It’s not uncommon because those who would embrace one pseudoscience are likely to follow the same flawed logic and process to accept others. My colleague David Gorski has termed this effect “crank magnetism.”

Take, for example, Gian Paolo Vanoli. He has been making international headlines recently because of his claim that vaccines cause homosexuality, which he insists is a disease. The story appears to have been first picked up in English by the Huffington Post – all other reports of this story I have found cite this article as their source.

Because of the date of this article (4/1) I wanted to make sure I had another source, but the only other sources are in Italian. The story does seem to check out – here is one article: Gian Paolo Vanoli: Cricket on the urine that has been around the world. 

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Feb 16 2012

Mercury Still Not Correlated with Autism

Published by under autism,Neuroscience

Another study, published recently in PLoS One, fails to show a correlation between mercury and autism. This was a study of mercury excretion in the urine, comparing subjects with autism to their siblings as well as controls without autism spectrum disorder (ASD), both in mainstream and special schools. They found no significant difference among the groups, even controlling for kidney function (creatinine clearance), age, gender, and amalgam fillings.

To put this study into context – there are those who claim that mercury toxicity is what causes ASD, and in fact ASD is simply misdiagnosed mercury toxicity. There is no question that mercury is indeed a neurotoxin, but toxicity is all about dose, so the question is are children being exposed to mercury in high enough dose to cause toxicity. Further, it is difficult to extrapolate from preclinical studies (in test tubes and petri dishes) to living organisms. We need to further know what happens to the toxin in the body, and how the body handles it.

With regard to the forms of mercury found in some vaccines (although much less than in previous years) and tuna fish, the body seems to rid itself of the mercury sufficiently quickly to prevent build up to toxic levels. Of course, this remains a hot topic because of the persistent claims by the anti-vaccine movement that vaccine cause ASD, and some who cling to the discredited notion that it is mercury in vaccines that is the culprit. There are also the so-called “mercury militia” who blame environmental mercury (from vaccine and elsewhere) on all human illness, not just autism.

As further background, it’s helpful to note the chain of argument that has occurred with respect to the role of mercury in autism. Studies have consistently found no correlation between mercury exposure and the risk of ASD. Proponents of the mercury hypothesis have therefore argued that there is a subpopulation of vulnerable children who metabolize and excrete mercury differently than the general population, and it is within this subpopulation that mercury causes ASD.

Logically this may be true, but the argument is little more than special pleading, although a common one. Scientists are familiar with the usual list of special pleading arguments made to dismiss negative evidence. These include: that the dose studied was too low, the treatment duration was too short, the placebo or comparison treatment was also effective, or the looked-for effect only exists in a subpopulation. Each one of these arguments is logically consistent – if true they would explain the negative results without meaning that the phenomenon is not true. They may even be true in specific cases. What makes them special pleading is when they are invoked ad hoc to explain negative evidence without good justification.

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Dec 28 2011

What Is an Antivaxer?

(Cross-posted at Science-Based Medicine.)

Labels are a cognitive double-edged sword. We need to categorize the world in order to mentally capture it – labels help us organize our mental maps of the overwhelming complexity of things and to communicate with each other. But labels can also be mental prisons, when they substitute for a thorough, nuanced, or individualized assessment – when categorization becomes pigeon-holing.

We use many labels in our writings here, out of necessity, and we try to be consistent and thoughtful in how we define the labels that we use, recognizing that any sufficiently complex category will be necessarily fuzzy around the edges. We have certainly used a great deal of electrons discussing what exactly is science-based medicine, and that the label of so-called alternative medicine is really a false category, used mainly for marketing and lobbying (hence the caveat of “so-called”).

We get accused of using some labels for propaganda purposes, particularly “antivaccinationist” (often shortened to “antivaxer”). Also “denier” or “denialist”, as in germ-theory denier. Even though we often apply labels to ourselves, no one likes having an unflattering label applied to them, and so we have frequent push-back against our use of the above terms.

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