Preservatives in vaccines are a good thing. They are added to prevent bacteria from contaminating the vaccine during the manufacturing process and later on as the vaccine is administered to the patient.

The standard preservative used in vaccines from the 1930s was mercury, because it is highly effective in killing bacteria and viruses. But in high doses, mercury can cause damage to the brain, heart, kidneys, lungs and immune system. It can also harm the developing nervous system of growing children.

In 1999 the American Academy of Pediatrics recommended that the FDA remove mercury from childhood vaccines in the US. And by 2001, a preservative called thimerosal, which contains mercury as the active ingredient, was largely removed from most adult and pediatric vaccines.

But because mercury is so effective, the FDA still permits limited use of thimerosal today in some childhood vaccines and in multi-use flu vaccines for both children and adults.

Mercury Exposure in Childhood Vaccines

Trace amounts of mercury (1 mcg or less per injection) are considered safe by the FDA, CDC and NIH, and may be present in some routine childhood vaccinations. However, children who are injected with multiple vaccines in a single visit or over a short period of time may accumulate several doses of mercury at once.

Reduce exposure

  • Trace amounts of mercury are processed and eliminated by the body, so parents can reduce the accumulation of mercury in their child’s body by spreading vaccinations over a longer period of time.
  • Speak with your doctor about creating a longer schedule for vaccines, so your child’s body has time to process and eliminate the first round of mercury before the next round is administered.

Mercury Exposure Through Flu Shots

Flu shots are often packaged in multi-use vials, which means that a single vial contains enough vaccine to treat multiple patients. A fresh needle is used for each patient, but because the vial is pierced multiple times, there is an increased chance for contamination. As a result, more thimerosal is needed for multi-use vials, exposing each flu shot patient to a higher dose (up to 25 mcg) of mercury.

Reduce exposure

  • Packaging flu shots in a multi-use vial can significantly lower the cost of the vaccine, making it more affordable for patients. The higher measure of mercury is still considered safe, but concerned parents and patients can reduce their exposure by paying a premium for single-dose flu shots.
  • Alternatively, patients from 2 to 49 years of age may be a candidate for thimerosal-free flu shots administered as a nasal spray. As with most drugs, the nasal spray flu vaccine may not be suitable for everyone and may not cover all strains of the virus. The CDC offers a list of who may be eligible.
  • The CDC also offers this list of available flu shots and their associated mercury levels. You may be able to choose a shot that is lower in mercury, if your doctor or pharmacy carries it.
  • Skipping the annual flu shot isn’t for everyone, but it is one way to avoid mercury altogether.

Good To Know

Vaccines labeled as “thimerosal-free” or “mercury-free” may still retain trace amounts of mercury left over from the manufacturing process, even if the preservative was not directly added as an ingredient. These trace amounts are considered safe by the FDA, CDC and NIH.

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