Last post, we left you with the question, "What is Thimerosal anyway?"
Here's some information that will shed light on this question...
What is thimerosal?
Thimerosal is a preservative that is used in many medications, including vaccines. It's popular because it is one of the few preservatives that can be used in a medication without altering the effect of the medication. It is approximately 50% mercury by weight. The human body breaks it down into ethylmercury and thiosalicylate.
The problem is that no one really seems to know what the biological effects of these two breakdown products are upon the human body, or if they're consistent between different human beings.
Until quite recently, there was very little research done on ethyl mercury. Most of the research has been focused on methyl mercury. All initial safety research on thimerosal was based on that methyl mercury, since it is so similar. All current research indicates that ethyl mercury is less toxic than methyl mercury and more easily excreted from the body. And then there's thiosalicylate. The chemical name for asprin is acetylsalicylic acid. It's been noted for some time that certain individuals are allergic to asprin.
More recently, there's been research indicating that certain individuals are allergic or sensitive to all salicylates, including ones normally occurring in food. As far as I can tell, however, no one has done much research into whether the thiosalicylate created in the breakdown of thimerosal can be problematic for those sensitive to salicylates.
Please remember that science changes and the information in this section is based on a very brief survey of easily located research. If you are interested in the metabolism of thimerosal, the excretion of the breakdown products, and the variability between individuals in these areas, I strongly keeping up to date on the current research. There's an extraordinary amount of work being done in this area right now.
Why do we need preservatives in vaccines?
In 1928, a diphtheria vaccine was being distributed from a multi-dose vial. (This means that there is a bottle filled with the serum and you withdraw multiple doses from the bottle...allowing for possible contamination when the needle is inserted into the bottle). The first 21 vaccinations were given without problems. At that point, the vaccine became contaminated with staph bacteria. Of the next 21 vaccinations from that vial, 11 children died from staph infections. Preservatives were added to multi-dose vials to prevent a repeat of that tragedy.
Is thimerosal still in vaccines? What about other pharmaceuticals?
Preservatives are not required in single-dose vials of vaccines, since there is no opportunity for the vaccine to become contaminated. Single-dose vials of vaccines are slightly more expensive to manufacture, however. In 2000, after increasing concern about thimerosal, the US began eliminating multi-dose vials of vaccines (and the thimerosal) from vaccines. Most vaccines these days are distributed from single-dose vials, especially the ones intended for children. The injectable flu vaccines are offered in multi-dose or single-dose vials. The multi-dose vials are cheaper. The single-dose vials have no thimerosal in them, but are slightly more expensive.
If you're sensitive to (or concerned about) thimerosal, please remember to check other pharmaceutical products besides vaccines. This preservative is found in many brands of eye drops and nasal sprays.
So, if all children get basically the same vaccine, with the same ingredients, and their reactions vary...what might be causing this? Well, in such a scenario, the only variables appears to be either (1) the batch of the vaccine (yes, batches can be different, just like all pharmaceutical drugs - and recalls do happen on occasion) or (2) the children themselves.
Next post, we will address variability in how humans excrete heavy metals.