Home > News > Thimerosal: It doesn’t cause autism, and it’s not even in our vaccines, which also don’t cause autism

Thimerosal: It doesn’t cause autism, and it’s not even in our vaccines, which also don’t cause autism

by Pete Souza via The White House

Yet another addition to the burgeoning mountain evidence of vaccine safety: early exposure to thimerosal doesn’t cause autism. You may remember that thimerosal was targeted by the anti-vaccination autism advocates as a dangerous mercury-containing agent that caused brain damage in children who were victims of vaccination. At face value, it seems natural to be concerned about exposing our children to mercury. The autism concern with thimerosal, however, was misplaced from the beginning, as it ignored at least one key fact: the vaccine most railed against by autism/vaccine crusaders, MMR (measles, mumps, rubella), NEVER contained thimerosal. Secondly, due to (this misplaced) concern regarding its safety, vaccine manufacturers began removing thimerosal from their products in 1999. Lo and behold, autism rates have continued to climb. You don’t have to be a scientist to follow the logic here.

Of course, we are only discussing this because there is still significant public campaigning against vaccines. This despite the nearly two dozen studies, many large and well-designed, that have consistently shown the absence of a link between vaccination and autism. Compare this with the only high-profile study to claim to demonstrate a link, which was retracted by the journal and renounced by all but one of its authors, who appears to be the least credible of the group.

Why was thimerosal removed from the vaccines, then? In developed countries it is not necessary as a preservative. It continues to be an important ingredient in vaccines used in developing nations where extended and poorly-controlled storage of vaccines is more common. And the American Academy of Pediatrics felt there was little to no downside to requesting its removal. This was true from a medical point of view. From a political perspective, however, this was apparently a mistake: the call for removal of thimerosal by a mainstream medical body gave fuel and a flash of credibility to the growing anti-vaccination movement. Since then, many resources, including high-profile celebrity advocacy, that could have been helpful in making real progress toward understanding, treating, and preventing autism have been diverted.

This all wouldn’t be so bad if it were just typical scientific wheel-spinning while research found its appropriate direction. There is real damage being done, however, to the credibility of vaccination as a whole. I believe that vaccination is the single most important innovation in medical practice ever (even more important than the beloved draw-a-clock test!). One of the secrets of medicine, which is rarely brought to attention, is that we cure almost nothing: infections, some cancers, and some problems amenable to surgery. Heart disease? COPD? Dementia? Hypertension? Schizophrenia? In most cases, the best we can do is to manage it. People can do very well, but at the cost of indefinite treatment. How can we decrease the overall disease burden the best? Keep people from getting sick in the first place. And the best way to do that is: diet and exercise. OK, so we need a more practical recommendation. The answer is vaccination!

Vaccines prevent deadly and debilitating disease. Vaccines do not cause autism. Are there risks to getting vaccinated? Yes, but they are much lower than the risks of NOT getting vaccinated. EVEN IF vaccines are the sole cause of autism, WHICH THEY AREN’T, it would still be worth getting vaccinated. Don’t believe me? Ask Penn & Teller.

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  1. September 16, 2010 at 1:44 pm

    Thank you for saying succinctly what i have been trying to communicate for years.

  2. September 19, 2010 at 11:23 am

    IIRC the reason thimerosal was removed from American vaccines was because the FDA noticed that some children (I guess the ones than weighed the least) could be being exposed to greater than the nominal “safe threshold” for mercury in mg/kg, as a result of the vaccine schedule.

    Of course that doesn’t mean it was a dangerous level because the thresholds are arbitrary and are deliberately set to be conservative. But it caused a lot of hoo-hah in the long run.

    • September 19, 2010 at 11:11 pm

      I believe that’s right. A quick review of the FDA page on thimerosal notes that it is metabolized to ethylmercury. Methylmercury (not ethyl) is a known neurotoxin, so they used the guidelines for dosing of methylmercury to assess toxicity of thimerosal. I couldn’t find any mention of a reported adverse effect from thimerosal except at doses hundreds or thousands times the dose ever found in vaccines. But I think that there are now some alternatives, and the FDA felt that they shouldn’t give kids mercury if they had another choice, which makes sense. It was the right thing to do, but the reasons were, I believe, misinterpreted.

  3. November 4, 2010 at 1:43 pm

    I had grilled swordfish for dinner last night and a flu shot a month ago. I’ll let you guess which one had more mercury… I enjoyed the swordfish more than the flu shot, it must have been the mercury which adds a certain tang to the meat.

    If you are nervous about thimeresol, and there is no reason to be nervous about it, skip one swordfish and get 500 flu shots. You will be ahead in mercury exposure this way and protected from flu. Also the swordfish is an expensive dinner.

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