Congress has asked for a new investigation into a potential link between mercury-containing vaccines and autism, as some lawmakers claim the Centers for Disease Control and Prevention has inadequately researched the topic.
"If the federal government is going to have a study whose results will be broadly accepted, such a study cannot be led by the CDC," Sen. Joseph Lieberman, D-Conn., and seven other members of Congress wrote in a letter to the National Institute of Environmental Health Sciences (NIEHS).
A budget appropriation approved by Congress urges the NIEHS to examine the Vaccine Safety Datalink, a CDC database that follows 7 million immunized children from 1990 to the present.
Some lawmakers believe a new review of this database may show a link between autism and thimerosal -- a vaccine preservative containing mercury.
A local parent who said he believes his two autistic children were harmed by vaccines applauded Congress for requesting a new investigation. The parent, Jared Hansen of Framingham, said he thinks the CDC is reluctant to expose dangers of thimerosal because the agency is responsible for ensuring public acceptance of its vaccination program.
"They've proven far more willing to overstate the risks of disease and understate the danger of vaccination," Hansen said. "No one in their right mind can say that giving mercury intravenously is a smart thing to do."
Autism rates soared during the 1990s when thimerosal was most heavily used in childhood vaccines. Levels of mercury injected into infants were 120 times greater than federal safety limits for oral ingestion of mercury, congressmen wrote to the NIEHS.
Government officials asked manufacturers in 1999 to remove the mercury-based preservative from vaccines, but it is still used in flu and tetanus shots.
CDC's research on the Vaccine Safety Datalink is flawed, Lieberman and his colleagues wrote, because it "was based on data collected prior to the removal of thimerosal and failed to explicitly compare the outcome of children who received thimerosal-containing vaccines with those who did not."
The CDC refused to comment on the criticism of its research.
But Dr. Marie McCormick, a Harvard professor who chaired an Institute of Medicine committee in 2004, said the group ran several analyses of the CDC data and found no link between thimerosal and autism.
"Nothing you could do changed the results," McCormick said. "The results of the...study have been replicated in England. They found no association between thimerosal and other neurodevelopmental disorders."
In the letter to NIEHS, members of Congress criticized the IOM for relying heavily on European data, even though American children were exposed to mercury at levels 75 percent greater than in Europe.
The letter was not signed by any Massachusetts congressmen. But U.S. Rep. Martin Meehan, D-5th, said he agrees with its content and would have signed on had he been aware it was being written.
"Mercury is known as a brain poison and in the 1990s a greater number of children were being exposed to mercury (in vaccines)," Meehan said. "I think this is a serious public health concern and we need more research."