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IOM Scrutinizes Link Between Vaccines, Neurological Problems

July 19, 2001By Mindy Hung New York - Amidst concern about mercury content in
vaccines commonly administered to children and a possible link to autism and
attention deficit hyperactivity disorder (ADHD), the Institute of Medicine
convened a meeting of their Immunization Safety Review Committee, in
Cambridge, Massachusetts, on Monday. The multidisciplinary committee, chaired
by Marie McCormick, MD, ScD, of the Harvard School of Public Health, has been
charged with assessing a possible causal relationship between inoculations
and adverse health consequences, and disseminating the results of the
assessment to the public. Immunizations for Haemophilus influenzae type b
(Hib), hepatitis B, diphtheria, and tetanus toxoids with acellular pertussis
(DTaP) have been a source of controversy in recent years because they use
thimerosal, a preservative containing low levels of ethylmercury (EtHg),
which can cause neurological damage. Pregnant women and fetuses are at
highest risk from exposure. The metal is excreted from the body over time.
However, according to a review conducted by the Food and Drug Administration
in 2000, infants younger than 6 months may accumulate EtHg at levels that
exceed federal safety guidelines established for the intake of another highly
toxic mercury, methyl mercury, which occurs naturally in seafood. Exposure to
large amounts of metallic, inorganic, or organic mercury can permanently
damage the brain, kidneys, and a developing fetus. Irritability, shyness,
tremors, changes in vision or hearing, and memory problems may
result. Although thimerosal has been used in biologics since the 1930s, an
increased number of vaccinations combined with a sharp rise in reported
autism and ADHD incidence has caused parents and some physicians to question
the safety of the inoculations. Preliminary data from Centers for Disease
Control and Prevention in Atlanta, Georgia, suggests a weak correlation
between vaccine-related thimerosal exposure and incidence of language and
speech delays, along with other neurological problems. In a joint statement
made in July 1999 and finalized in June 2000, the American Academy of
Pediatrics, the US Public Health Service, and others emphasized that the
risks of not vaccinating children far outweigh the possible problem of
cumulative exposure to thimerosal. They note, however that "because any
potential risk is of concern, and the elimination of exposure to mercury in
the form of thimerosal from vaccines is feasible, thimerosal should be
removed from vaccines as soon as possible." Except for DtaP, thimerosal-free
versions of pediatric vaccines are available. The measles-mumps-rubella
vaccine, which has been implicated in the rise in cases of autism, does not
contain thimerosal. The Immunization Safety Review Committee will release its
findings on its Web site. Mindy Hung is an associate editor at
Medscape.MedscapeWire is edited by Deborah Flapan, an associate editor at
Medscape. Send press releases and comments to medscapewire2@medscapeinc.com.

ALL INFORMATION, DATA, AND MATERIAL CONTAINED, PRESENTED, OR PROVIDED HERE IS FOR GENERAL INFORMATION PURPOSES ONLY AND IS NOT TO BE CONSTRUED AS REFLECTING THE KNOWLEDGE OR OPINIONS OF THE PUBLISHER, AND IS NOT TO BE CONSTRUED OR INTENDED AS PROVIDING MEDICAL OR LEGAL ADVICE.  THE DECISION WHETHER OR NOT TO VACCINATE IS AN IMPORTANT AND COMPLEX ISSUE AND SHOULD BE MADE BY YOU, AND YOU ALONE, IN CONSULTATION WITH YOUR HEALTH CARE PROVIDER.