Infant study casts doubt on vaccine-autism link

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - The mercury in a vaccine preservative is pumped out of a baby's body too quickly for it to do any damage, researchers reported on Wednesday in a study they say should further absolve shots of causing autism.

The study in the journal Pediatrics reinforces what many vaccine experts have said for years -- that the form of mercury found in the preservative is handled differently by the body than the kind found in pollution and contaminated fish.

"It takes a certain amount of time and a certain concentration ... to make it into the brain," Dr. Michael Pichichero of the University of Rochester in New York, who led the study, said in a telephone interview.

Thimerosal is widely used to preserve vaccines and is made from a kind of mercury called ethyl mercury. It allows vaccines to be distributed in multi-dose containers.

"The World Health Organization has continued to sanction the use of thimerosal in vaccines because it has proven to save many lives by preventing bacterial contamination," said Pichichero, who has served as a consultant to several vaccine manufacturers and the WHO.

Many studies have shown thimerosal is safe, but some vocal groups have continued to lobby against its use and it has been removed from all childhood vaccines in the United States except for some influenza vaccines.

Pichichero's team studied 216 infants from R. Gutierrez Children's Hospital in Buenos Aires, Argentina, where thimerosal is still routinely used in vaccines.

They were divided into three age groups to have their blood-mercury levels tested before and after they were immunized at their newborn, 2- or 6-month checkups.