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Persistent concern about the safety of
vaccinations prompted the US National Academy of Sciences
Institute of Medicine to convene an open public meeting in
Cambridge, Massachusetts, on July 16, to review the evidence
for an association between thimerosal, a mercury-containing
preservative found in multidose vaccine preparations, and
neurodevelopmental outcomes, particularly autism, the prevalence
of which has apparently increased over the past decade.
Thimerosal, also known as ethylmercury,
has been used as a preservative since 1930, and is now hypothesised
to carry similar risks as methylmercury, a chemical that is
known to be toxic in animals and human beings.
In June, 1999, the American Academy of
Pediatrics and the US Public Health Service, acknowledging
that mercury exposure from vaccinations given in the first
6 months of life exceeded maximum acceptable levels established
in federal guidelines, called for a halt to the manufacture
of thimerosal-containing vaccines. Although no longer routinely
given in the USA (European and UK regulators have also recommended
phasing out their use), they are still the norm in many other
parts of the world, especially in developing countries.
Neal Halsey (Johns Hopkins University,
Baltimore, Maryland, USA) said that all countries
need to stop using these vaccines now, but single-use
vaccines, carrying added costs for storage, production, alternative
preservatives, and quality control measures, are prohibitively
expensive for developing countries.
The meeting was the third in a series
of gatherings hosted by the IOM's Immunization Safety Review
Committee, an independent expert group established by joint
request of the Centers for Disease Control and Prevention
and the National Institutes of Health.
In its report, to be issued within 90
days of the meeting, the committee will recommend public health
responses for surveillance, research, and policy. It will
consider, in addition to the evidence for causality, the biological
plausibility of adverse events, and will explore the social
and cultural context of the issue.
Lancet July
21, 2001; Volume 358, Number 9277
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