Magazine article Science News

Lack of Evidence: Vaccine Additive Not Linked to Developmental Problems

Magazine article Science News

Lack of Evidence: Vaccine Additive Not Linked to Developmental Problems

Article excerpt

A mercury-containing vaccine preservative is not associated with problems in speech, intelligence, memory, coordination, attention, or other measures of childhood development, a large new study finds.

Child-health experts say that the results should allay concerns that thimerosal, a preservative first added to vaccines in the 1930s, affects children's brains.

"The study was enough to convince me that this small amount of mercury ... was not harmful to the children," says Michael Goldstein, vice president of the St. Paul, Minn.-based American Academy of Neurology.

"I think it's one more piece of evidence that thimerosal doesn't have any negative association with health outcomes," says Penelope Dennehy, professor of pediatrics at the Brown University School of Medicine in Providence, R.I.

The study, funded by the Centers for Disease Control and Prevention (CDC) in Atlanta, enrolled 1,047 children, from 7 to 10 years old, whose health needs had been covered from birth by four health maintenance organizations. The researchers combed the health plans' records to assess how much thimerosal each child received through the first 7 months of life.

Each child took a battery of 42 tests of language, memory, motor coordination, attention, and intelligence. The researchers then attempted to correlate the amount of mercury each child received--from 0 through 187.5 micrograms--with performance on the tests.

"We found no consistent pattern between increasing mercury exposure ... and performance on neuropsychological tests," CDC epidemiologist William W. Thompson and his team say in the Sept. 27 New England Journal of Medicine.

However, of 378 different statistical measures derived from the test results, 19 did show some small associations with thimerosal exposure. Twelve such measures were positive--that is, higher thimerosal exposure led to better outcomes--while seven were negative. …

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