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Jan. 9, 2003

By Mary Pickett, M.D.
Harvard Medical School

How does this article relate to me?

The two-paragraph provision that these parents are protesting is a part of the 475-page bill that was designed to establish and organize the new Office of Homeland Security for the United States. This last-minute provision provides vaccine-makers with an incentive to plunge ahead into new vaccination development and research initiatives by protecting them retroactively against lawsuits relating to the preservative "thimerosal." Thimerosal exposure from certain infant vaccinations has been speculated by some people — but not proven — to cause autism or attention deficit hyperactivity disorder (ADHD). This provision removes lawsuits related to thimerosal from state courts, limits the compensation for damages in any of these lawsuits to $250,000, and promises to fund that compensation money out of an account that is funded by taxpayers.

One of the justifications that pharmaceutical companies provide for the high cost of drugs is the high price they must pay to insure their corporation against unforeseen liability. This is not the job of the taxpayer. Singling out one corporation or industry for protection does not make sense.

The thimerosal claims are based on very incomplete evidence, but there is some scientific basis behind the worries. This preservative is broken down in part to a form of organic mercury, ethylmercury. Ethylmercury is chemically very similar to methylmercury, an organic mercury that is known to cause nerve injury. Exposures of a large group of pregnant women to methylmercury after an agricultural contamination event apparently caused a condition in their infants resembling cerebral palsy. Mercury has long been known to cause brain injury. In fact, the popular "Mad Hatter," character of "Alice In Wonderland" was based on the frequent psychotic symptoms experienced by hat makers in the 1800's, when they used solutions of mercuric nitrate to shape felted wool hats.

Today, we are exposed to mercury from many sources in our daily lives. Federal and world health agencies have developed guidelines that estimate a safe exposure limit to the most commonly encountered organic mercury, methylmercury. Concerns about thimerosal (ethylmercury) emerged when it became apparent that with increased vaccination practices, some children were exposed to a level of ethylmercury that was equal to or higher than the recommended maximum exposure limit for methylmercury. The U.S. Public Health Service Agencies have recommended removal of thimerosal from childhood vaccines to ensure safety, although no definite harm from it has been established.

What changes do I need to make?

It is reasonable to take some precautions to limit mercury exposure from your environment.

• If you are pregnant or breast-feeding and you are receiving a flu shot, request a preparation that either is thimerisol-free or contains trace quantities of thimerosal ("thimerosal-reduced.") These vaccines are widely available through pediatric clinics.
• Notify your doctor if you have a local reaction before receiving any additional vaccination. Independent of mercury issues, thimerosal in adult vaccinations can cause a local allergic reaction of redness and swelling at the vaccine site.
• If you are anticipating pregnancy, are pregnant or breast-feeding, or if you are a young child, the U.S. Food and Drug Administration recommends that you avoid certain types of fish — shark, swordfish, king mackerel, and tilefish — because they accumulate worrisome amounts of methylmercury.
• Limit the number of mercury-containing products in your home. Dispose of mercury-containing products through your local hazardous waste program rather than in your regular trash.

Household products that contain mercury include:

• Some lighted children's athletic shoes
• Indoor paint made before 1990 and outdoor paint made before 1991
• Alkaline batteries and some "button" batteries for watches and calculators
• Fluorescent and high intensity discharge light bulbs
• Gardening anti-fungal sprays or additives
• Thermometers with a red bulb (Digital thermometers do not contain mercury)
• Some old dental fillings
• Non-electronic thermostats and switches

What can I expect in the future?

Currently, all of the vaccinations that are routinely provided to infants are either free of thimerosal or they contain only a trace amount of the preservative. One of the trends that has allowed for reduced preservative exposure has been the manufacture of "single-use vials" for vaccination solutions, so that a preparation may remain sterile without such additives. Fortunately, the number of vaccines that are required for children is being reduced by another trend, the development of combination vaccines. By reducing the number of vaccines, they will reduce the quantity of preservatives (thimerosal or other) to which a child is exposed. The latest new available vaccine for children is a combination vaccine that protects against diptheria, tetanus, pertussis, polio, and the hepatitis B virus all at once. This vaccine will reduce the number of vaccines that used to be required to protect children ages 3 to 9 against all of these infections.

Related Areas:

U.S. Food and Drug Administration: Frequently Asked Questions about Thimerosal
Childhood Vaccines: What Every Parent Should Know