Vaccinations and Autism – Linked or Not Linked? Part II of III

su Vaccinations and Autism – Linked or Not Linked?  Part II of III

So, in my last post I discussed what vaccines were, what types of  vaccines there are, and what they are composed of (different substances you might find in a vaccine).

In this post, I will address the more controversial points about vaccination – do they cause serious diseases, and most of all, is there a link between vaccinations and autism.  I will be referencing several sites and journals as I go (since this IS an evidence-based blog! ;) , and you’ll find all of those references at the bottom.Vaccine shot thumb Vaccinations and Autism – Linked or Not Linked?  Part II of III

Vaccines have been under fire almost since they were first invented, for causing all sorts of ill effects.  Sometimes this has drastically altered the face of public health policy.  In the United States, there has been an outcry from antivaccinators targeting a link between vaccines and autism.  Specifically, most of the attacks on vaccinations are on two things:  thimerosal containing vaccines, and the MMR (measles, mumps, rubella) vaccine.

Thimerosal is a preservative that was widely used in vaccines in the US until 1999, at which time it was voluntarily removed from the vast majority of vaccines (really the only vaccines that contain thimerosal now are the seasonal flu shots, in multi-dose vials).  Thimerosal is supposed to be dangerous to children’s health due to the fact that it contains mercury.

It is important to note that thimerosal doesn’t contain the solid metal mercury (OK, it’s a liquid, but you get the point).  It actually contains a substance called ethylmercury, which is eliminated from the body much faster than regular mercury is.  Here is what one study in the Journal of the American Medical Association discovered about thimerosal and autism:

“We found no evidence of an association between thimerosal-containing vaccine and autism in children who received thimerosal-containing vaccine compared with children who received the same vaccine formulated without thimerosal. Furthermore, there was no indication of a dose-response association between autism and the amount of ethylmercury received through thimerosal.

The hypothesis of an association between thimerosal and autism has primarily been based on biological plausibility through analogies with methylmercury.2 Ethylmercury, however, is thought to have a shorter half-life in the human body than methylmercury, and no controlled studies of low-dose ethylmercury toxicity in humans have been conducted.11 Pichichero and colleagues12 measured the concentration of mercury in the blood, urine, and stool of infants who received thimerosal-containing vaccines and concluded that vaccination did not raise the blood concentration of mercury above safe limits, and that ethylmercury was rapidly eliminated via the stools. They estimated the blood half-life of ethylmercury at 7 days (95% CI, 4-10 days), although their study was not designed as a formal pharmacokinetic study of ethylmercury(1).”

Well, that was quite a lot of words.  First of all – they found no evidence that thimerosal containing vaccines cause autism. The second paragraph talks about the substance I mentioned before, ethylmercury, and talks about how they discovered that it is rapidly eliminated from the body, and in fact never approaches unsafe levels in the bloodstream.

In an excellent letter to the Journal of the American Osteopathic Association, Dr. KinKee Chung, DO writes:

“The origins of the supposed link between autism and the measles-mumps-rubella (MMR) vaccine can be traced to a 1998 article by Andrew J. Wakefield, MD, and colleagues.2 Although that article no longer has any scientific merit, the hypothesis of the autism-vaccine link has become deeply rooted among many parents who have children with autism. To this day, these parents accuse the MMR vaccine, thimerosal (a mercury-containing preservative formerly used in many childhood vaccines), or merely “many shots” of causing the onset of autism in their children. To such individuals, it does not matter how many scientific studies disprove the alleged associations or how much money was spent to conduct those studies. Thus, we are witnessing a disaster in public health caused by Dr Wakefield’s unsupported claims(2).

Dr. Chung also discusses an unrelated theory, that ultrasound can cause autism.  It’s quite an interesting letter.

Basically, Dr. Wakefield (mentioned above in the letter) did a study where he discovered a link between autism and vaccinations.  Many years after the study, it was discovered that he had massive conflicts of interest, and falsified information in his paper.  10 of the 13 authors of the paper retracted what they had said.  You can read a little more about Wakefield on Wikipedia (I usually don’t use Wikipedia, but it actually has a good write-up on Wakefield)(3).

Unfortunately, as fears about autism rise, vaccination rates have declined.  We are now seeing outbreaks of illnesses that were nearly destroyed.  Many people that are against vaccines might say that the illnesses themselves aren’t all that bad, but children have died (and recently, due to declining vaccination rates) from measles, whooping cough, etc.

Not enough is being done to get new scientific findings out to the general public.  This is one of the purposes of this blog – to try to get the word out (in a *hopefully* understandable way) about new studies,  especially those that disprove things or uphold public health studies.

I realize that this article also is decidedly one-sided.  I must admit to a slight bias in this area, since I feel that vaccines are absolutely necessary.  I feel that you should know about my bias, so you can make your own decision.

That being said, I spent quite a lot of time researching this particular topic for the sake of presenting evidence concerning both sides.  Had there been any evidence pointing to a link between autism and vaccinations, I would have presented it – but, to date, I have not found any published in peer-reviewed journals.  In trying to present the best evidence possible, I wanted to only use scientifically tested evidence for this article.

Please, feel free to comment if you have something to add, or ask any questions.  Until next time (which will be part III of this series)!

References

(1) Anders Hviid, MSc; Michael Stellfeld, MD; Jan Wohlfahrt, MSc; Mads Melbye, MD, PhD.  Association Between Thimerosal-Containing Vaccine and Autism.  Journal of the American Medical Association – 2003:290:1763-1766

(2) Chung, KinKee, DO.  Letter to the Editor.  Journal of the American Osteopathic Association – July 2009, Vol 109, No 7, 384-386.

(3) Wikipedia:  Andrew Wakefield.  Accessed on 3/2/2010.  http://en.wikipedia.org/wiki/Andrew_Wakefield.

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One Response to “Vaccinations and Autism – Linked or Not Linked? Part II of III”

  1. [...] first article, I talked about what vaccines are, and what types of substances are in them.  In my second article, I discussed the possible link between autism and vaccinations.  In this article, the final part [...]

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