US study finds no link between vaccines and autism

ATLANTA - Researchers say they have found no significant link between childhood vaccines containing mercury-based preservative thimerosal and neurological problems such as autism and attention-deficit disorder in a study of more than 140,000 kids.

But critics charged that the study, which was published in the November, 2003 issue of Pediatrics, had been manipulated to protect the federal government and vaccine manufacturers from embarrassment and potential lawsuits.

Thimerosal, an organic compound that is 49 per cent mercury, was used routinely in the United States between the 1930s and the 1990s to prevent bacterial and fungal contamination of a wide range of infant vaccines, including hepatitis B.

The American Academy of Pediatrics and the US Public Health Service recommended removing it from childhood vaccines in 1999 as a precaution. Studies have linked ingestion of mercury to neurological and renal problems in humans.

In a study of records from three US health management organisations, researchers from the Centres for Disease Control and Prevention and the private sector found conflicting data when they screened for a connection between vaccines and neurological disorders in children born between 1991 and 1999.

One group of children who had received routine vaccines containing thimerosal had a higher incidence for tics, while a separate group had a higher rate of language delays, according to the study.

A second phase of the study showed no significant links to such problems in another group.

"The final results of the study show no statistical association between thimerosal vaccines and harmful health outcomes in children, in particular autism and attention-deficit disorder," said Dr. Frank DeStefano, a CDC researcher who helped carry out the study.

But public health activists, including those who work with autism sufferers, said that neurological disorders had been found at significantly high rates in the original analysis of the study in 2000, but had been watered down in the final version.

In a statement released on Monday, Moms on a Mission for Autism accused CDC researchers and others of "conspiring to deliberately deceive the American people by minimising the ill-affects of thimerosal."

Critics also noted that Dr. Thomas Verstraeten, the lead author of the study, left the federal agency two years ago to join GlaxoSmithKline Plc., which manufactures vaccines. The article in Pediatrics failed to note that Verstraeten was employed by the European pharmaceutical giant.

"This revelation undermines this study further," US Rep. Dave Weldon, a Republican and physician from Florida, wrote in a letter to CDC Director Dr. Julie Gerberding. Weldon called for an independent review of the study.

A GlaxoSmithKline spokeswoman said the company had never asked Verstraeten to change the study's data.