Reuters
Oct 1 2001 3:58PM
WASHINGTON (Reuters) - There is no proof that a mercury-containing
preservative present in some vaccines causes developmental disorders in children,
but doctors should steer clear of giving children vaccines made with the
substance just to be safe, a panel of experts said in a report on Monday.
The report by a panel convened by the Institute of Medicine, which provides
advice on health issues to the U.S. government under a congressional charter,
focused on thimerosal, long used in some vaccines and other pharmaceutical
products to prevent bacterial and fungal contamination.
The committee concluded that no evidence currently exists proving a link
between thimerosal-containing vaccines and autism, attention
deficit-hyperactivity disorder, speech or language delays, or other
neurodevelopmental disorders.
But the panel said it is "biologically plausible" that some
children's risk of one of these disorders could be increased by exposure to
mercury from vaccines containing thimerosal, which contains nearly 50 percent
mercury by weight. The experts said existing evidence is insufficient either to
accept or reject the idea that vaccines containing mercury can cause these
childhood disorders.
Mercury, a heavy metal that can harm the nervous system, can build up in
the human body with each exposure, whether from vaccinations or other sources
such as contaminated fish.
Very few vaccines used in the United States still contain thimerosal and
many types of vaccines never contained it, the panel said. But the committee
recommended that, as a prudent precaution, vaccines that contain thimerosal not
be administered when there is an alternative.
"If a vaccine without thimerosal is available, it should be used.
However, if that vaccine is not available, it's far better to be vaccinated
with a thimerosal-containing vaccine than not be vaccinated," Marie
McCormick, a professor of maternal and child health at Harvard School of Public
Health who headed the Institute of Medicine committee, said in telephone
conference call with reporters.
"REAL, PROVEN THREATS"
Some health professionals have expressed alarm that some parents are
refusing to allow their children to receive recommended vaccines because of
concerns about mercury.
McCormick said childhood immunization is one of the most effective tools
for preventing millions of cases of disease and death. She said vaccines
protect against "real, proven threats to unvaccinated infants, children,
and pregnant women," while the health effects of thimerosal are uncertain.
The report was requested by federal health officials.
Thimerosal has been used in vaccines since the 1930s.
But the three-in-one vaccine against measles, mumps and rubella (also
called German measles) never contained the preservative, nor did the vaccines
for chicken pox or polio.
Several other vaccines recommended for children were made with thimerosal
until recently. The committee said these vaccines now are made without it, but
an unknown, probably small number of vaccine doses remain on clinic shelves.
They include vaccines for hepatitis B, diphtheria, tetanus and pertussis
(whooping cough), and haemophilus influenzae type B (Hib), a form of bacterial
meningitis.
A few vaccines, including influenza vaccine given annually during the viral
flu season to adults and some children, still are manufactured with thimerosal.
Thimerosal also remains in use in many other countries.
Two years ago, the federal government and leading medical organizations
urged new limits on mercury exposure of infants and young children -- a move
that instigated the development of routine childhood vaccines made without
thimerosal.
The panel urged that government agencies and professional societies review
their policies about nasal sprays, eye drops and other products that still
contain thimerosal and are used for infants, children and pregnant women.
Activists who have been critical of the mercury content in vaccines said
they were pleased the report acknowledged that it is plausible that
thimerosal-containing vaccines can cause neurological problems. Sallie Bernard
of the New Jersey-based group Safe Minds advocated the immediate recall of
remaining stocks of childhood vaccines containing thimerosal.
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