Q. Don't vaccines contain mercury, a known poison, as well as antibiotics?
A. Before the spring of 2001, several vaccines did indeed contain thimerosal, a mercury-based preservative used to thwart the growth of bacteria and fungi in vaccine vials. Fears about mercury stem from research that shows exposure to high doses can cause learning disabilities and damage the brain (which is why mercury is often blamed by those who suggest a connection between vaccines and autism). There's also the fear that it can compromise the immune system and kidneys. But according to the American Academy of Pediatrics (AAP), the ethyl-based mercury used in vaccines doesn't pose the same risk as methyl-based mercury (a known toxin found in fish and the environment that can damage the central nervous system). "Studies suggest that this is because the body can excrete ethyl-mercury more easily," says Dan Salmon, MD, associate director for policy and behavioral research at the Institute for Vaccine Safety at Johns Hopkins School of Public Health in Baltimore.
Nevertheless, ethyl-mercury can enter the central nervous system. So in an effort to reduce exposure to all forms of mercury, the AAP recommended in July 1999 that thimerosal be removed from vaccines as a precautionary measure. (The flu vaccine for children contains a tiny amount of thimerosal but it's considered safe.) Trace amounts of the antibiotic neomycin are added to some vaccines to help thwart the growth of potentially harmful bacteria in vaccine vials. But since allergies to this antibiotic are rare, it is considered safe.
Maureen Connolly is the coauthor of The Essential C-Section Guide (Broadway Books).
Originally published in American Baby magazine, February 2004.
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