A memo from Merck shows that, nearly a decade before the first public disclosure, senior executives were concerned that infants were getting...

A memo from Merck shows that, nearly a decade before the first public disclosure, senior executives were concerned that infants were getting an elevated dose of mercury in vaccinations containing a widely used sterilizing agent.

The March 1991 memo, obtained by the Los Angeles Times, said that 6-month-old children who received their shots on schedule would get a mercury dose as much as 87 times higher than guidelines for the maximum daily consumption of mercury from fish.

“When viewed in this way, the mercury load appears rather large,” said the memo from Dr. Maurice Hilleman, an internationally renowned vaccinologist. It was written to the president of Merck’s vaccine division.

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The memo was prepared at a time when U.S. health authorities were aggressively expanding their immunization schedule by adding five new shots for children in their first six months. Many of these shots, as well as some previously included on the vaccine schedule, contained thimerosal, an anti-bacterial compound that is nearly 50 percent ethyl mercury, a neurotoxin.

Federal health officials disclosed for the first time in 1999 that many infants were being exposed to mercury above health guidelines through routine vaccinations. The announcement followed a review by the U.S. Food and Drug Administration that was described at the time as a first effort to assess the cumulative mercury dose.

But the Merck memo shows that at least one major manufacturer was aware of the concern much earlier.

“The key issue is whether thimerosal, in the amount given with the vaccine, does or does not constitute a safety hazard,” the memo said. “However, perception of hazard may be equally important.”

Merck officials would not discuss the contents of the memo, citing pending litigation.

More than 4,200 claims against Merck and other drug companies have been filed in a special federal tribunal, the Vaccine Injury Compensation Program, by parents asserting that their children suffered autism or other neurodevelopmental disorders from mercury in vaccines. A handful of similar claims are awaiting trial in civil courts. The plaintiffs cite various scientific studies that they say prove the dangers of thimerosal, including at the levels found in vaccines.

Thimerosal has been largely removed from pediatric vaccines in recent years in what health officials have described as a precautionary measure. This has been accomplished as drugmakers have voluntarily switched from multidose vials of vaccine, which require a chemical preservative such as thimerosal, to single-dose containers.

Merck and other vaccine makers, along with many government health officials and scientists, say there is no credible evidence of harm from the amounts of mercury once widely present in children’s vaccines. They cite a report in May by a committee of the national Institute of Medicine concluding that the evidence “favors rejection of a causal relationship” between vaccines and autism.

The seven-page Merck memo was provided to the Los Angeles Times by James Moody, a Washington lawyer who works with parent groups on vaccine-safety issues. He said he obtained it from a whistle-blower whom he would not name.

The memo provides the “first hard evidence that the companies knew — or at least Merck knew — that the children were getting significantly more mercury [than the generally accepted dose],” the lawyer said.

He also provided a copy to attorneys for Vera Easter, a Texas woman who blames thimerosal for the condition of her 7-year-old son, Jordan, who is autistic and mentally retarded. The Easter lawsuit is pending in U.S. District Court for the eastern district of Texas. The defendants include Merck; rival vaccine makers GlaxoSmithKline, Aventis Pasteur and Wyeth; and thimerosal developer Eli Lilly.

Easter’s lawyer, Andy Waters, described the memo as “incredibly damning and incredibly significant.” After receiving it in the fall, he confronted Merck lawyers about why he hadn’t seen it earlier.

In a letter to Waters in October, Merck attorneys said they had in fact made available 32 boxes of records, but that the copying service hired by the plaintiffs for some reason had failed to copy several of the boxes, including the one with the Hilleman memo.

“The memo,” said company spokeswoman Mary Elizabeth Blake, “was produced voluntarily by Merck in the ordinary course of discovery proceedings.”

Hilleman is a former senior vice president of Merck who developed numerous vaccines for the company. A 1999 profile in The Philadelphia Inquirer said “it is no exaggeration to assert, as many scientists do, that Maurice Hilleman has saved more lives than any other living scientist.”

Hilleman, 85, currently director of the Merck Institute for Vaccinology, had officially retired and was a consultant to Merck when he wrote the ’91 memo. He declined to be interviewed.

The memo was sent to Dr. Gordon Douglas, then head of Merck’s vaccine division and now a consultant for the Vaccine Research Center at the National Institutes of Health. Douglas also declined to comment.