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recent backroom political maneuver that gave Eli Lilly protection against
lawsuits for damage allegedly caused by a mercury-containing preservative in
vaccines was not only an abuse of Congressional process. Its more pernicious
effect was to fan fears about the safety of vaccines and the ingredients used to
protect them from dangerous contamination.
The preservative in question, known as thimerosal, was used in many vaccines
to prevent microbial contamination until concerns were raised in 1999 that
cumulative doses of mercury might cause subtle harm to the developing brain.
Since then, thimerosal has been dropped from the vaccines routinely administered
to infants in America, but the issue remains important because thousands of
parents whose children had previously received mercury-containing vaccines have
filed damage claims or lawsuits alleging harm.
Although mercury is known to be toxic at high doses, there is very little
data on whether very low doses of ethyl mercury, the form found in thimerosal,
can be harmful. Last year the Institute of Medicine, an arm of the National
Academy of Sciences, concluded that the scientific evidence neither proved nor
disproved a link between thimerosal and neurodevelopmental disorders in
children. But this year the World Health Organization endorsed the preservative
for global use, concluding that there is no evidence of toxicity in infants,
children or adults exposed to thimerosal in vaccines. That judgment was
buttressed by an encouraging study published last Saturday in The Lancet, a
British medical journal. It found that vaccines containing thimerosal did not
raise the amount of mercury in infants above federal safety limits and that the
mercury was excreted quickly, suggesting that it would not accumulate with
repeated vaccine injections and cause damage.
Whatever risks might be posed by thimerosal are remote compared with the risk
from not getting vaccinated. That is why the American Academy of Pediatrics
recommended this week that infants as young as six months be given influenza
vaccine, which still contains small amounts of thimerosal. The academy said
healthy infants were at relatively high risk of hospitalization for the flu;
thus the benefits of vaccination "outweigh the theoretical risk of adverse
effects, if any, from the small volume of thimerosal" in the vaccine.
