Influenza vaccinations include the 49.6 percent mercury-containing preservative thimerosal, said Jeanne Santoli, deputy director of the Immunization Services Division of the Centers for Disease Control and Prevention.,”Though traces of mercury are found in most flu shots, experts say the dosage is not high enough to generate hazardous effects.

Influenza vaccinations include the 49.6 percent mercury-containing preservative thimerosal, said Jeanne Santoli, deputy director of the Immunization Services Division of the Centers for Disease Control and Prevention. When multiple doses of the vaccine are drawn from the same vial, thimerosal is used to reduce the risk of bacterial contamination, she said.

Santoli said the risk of contracting influenza is greater than the potential negative effects of thimerosal.

During an average year, 36,000 Americans die of the flu and flu related complications and more than 200,000 Americans are hospitalized, she said.

According to the CDC, exposure to mercury may have damaging effects on the digestive and nervous system and on the kidneys.

But Santoli said the amount of thimerosal in the influenza vaccination is too small and the benefits of getting a vaccine outweigh the theoretical risks.

Influenza vaccinations Fluzone, FluLaval and Fluvirin each have a thimerosal concentration of .01 percent, according to Food and Drug Administration reports. Fluarix has a concentration less than .00004 percent.

Santoli said no credible scientific studies have been conducted that show the amount of thimerosal to cause neurological problems.

Georges Benjamin, executive director of the American Public Health Association, said he agreed relative risks for the thimerosal dosage used in influenza vaccinations sit far below any signs of clinical risk.

Benjamin said it is more important to understand the difference between the ethylmercury used in influenza vaccinations and the methylmercury that is found in fish.

Ethylmercury is less toxic than methylmercury and used to preserve the influenza vaccinations, he said.

Methylmercury is the compound found in fish that is dangerous to humans after prolonged exposure, said Terri Goldberg, deputy director of the Northeast Waste Management Officials Association, a collaborative organization of waste and pollution prevention programs. Goldberg said she has done research on mercury levels in fish.

Methylmercury and ethylmercury are different types of mercury that have different effects with different levels of exposure, she said.

Methylmercury is a neurotoxin that is linked to autism in children and heart disease in adults, Goldberg said. But these effects will only come with prolonged exposure, she said.

Still, controversy exists over thimerosal levels in the influenza vaccination, Benjamin said. Efforts to create a thimerosal-free vaccination have stemmed from a precautionary principle, he said.

Santoli said all six influenza vaccine manufacturers who produce the vaccine for the United States market make at least some vaccine that is thimerosal-free or thimerosal-reduced.

Aurora Health Care's Shoo the Flu program offers a limited supply of thimerosal-free vaccinations at the Saturday clinics in West Allis, said Lisa Taylor, registered nurse and clinical coordinator for Shoo the Flu.

Few people receive the thimerosal-free vaccine, she said.

But the thimerosal-free vaccine protects against the same viruses as vaccines with thimerosal, she said.

"Getting a flu shot is the safest and most effective way to prevent the flu," Taylor said.

Because of the serious risk of influenza and lack of harm that comes from the small amount of thimerosal in vaccines, the CDC does not express a preference as to which type of vaccine patients should receive, Santoli said.

"The recommendations of CDC are appropriate and people should get their shots," Benjamin said. "The flu is vaccine-preventable."

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