In the past few years there has been a lot of discussion in the media regarding the presence of mercury in vaccines and the potentially dangerous effects of this. This fear, along with several other concerns, has led to a movement in which parents are refusing to vaccinate their children. The form of mercury that is present in vaccines, if any at all, is in a substance called Thimerosal.
What is Thimerosal?
Thimerosal is a mercury-containing organic compound that has been historically used as a preservative in many drug products including vaccines. The function of Thimerosal in these products is to prevent the growth of bacteria and fungi, which is a risk especially with multi-use vaccinevials. In fact, in the early days of immunizations there are multiple cases reporting the deaths of children that were vaccinated with injections that came from multi-dose vials that lacked a preservative.
After investigation it was determined that these children died because the vaccination vial had been contaminated and as a result a staphylococcus species of bacteria was injected into their bodies. Cases such as this emphasize the importance of using some form of preservative in our vaccines.
Why is Thimerosal dangerous?
Since Thimerosal contains mercury, it is associated with risks of being neurotoxic. Symptoms that are directly related to mercury exposure include neurologic dysfunction and developmental delays in children. These symptoms, however, have only been reported after injecting products that contained 3 mg/kg or more of Thimerosal.How is the FDA dealing with this issue?
In recent years Thimerosal has become known for potentially being neurotoxic, as a result the FDA has removed it from or reduced it to trace amounts in routine vaccines for children six and younger. A trace amount of Thimerosol is considered 1 mcg or less, which is significantly lower than 3 mg/kg which is the lowest reported dose of Thimerosal that has caused neurological side effects. According to the FDA (hyperlink), the one exception from this rule is the inactivated influenza vaccine which contains 12.5 mcg/0.25 mL dose. As an alternative option for patients that are at a slightly increased risk of Thimerosal toxicity (i.e. infants, pregnant patients and children), there is a preservative-free version of the influenza vaccine which only contains trace amounts of Thimerosal.
Integrate your Physician.
If you are concerned about the presence of Thimerosal in your annual influenza vaccine, or that of your children, ask your physician or pharmacist about the preservative-free version.
http://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/VaccineSafety/UCM096228