Washington ? Parents claiming that childhood vaccines cause autism should not be rewarded by the courts when the scientific community has already rejected any link, government lawyers argued Monday on the first day of a hearing in federal court.

Overall, nearly 4,900 families have filed claims with the U.S. Court of Claims alleging that vaccines caused autism and other neurological problems in their children. Lawyers for the families are presenting three different theories of how vaccines caused autism. The theory at issue Monday was whether vaccines containing the preservative thimerosal caused autism.

Lynn Ricciardella, a Justice Department lawyer, said that theory has not moved beyond the realm of speculation. She said that the Institute of Medicine and the Centers for Disease Control and Prevention have rejected any link between thimerosal and autism.

“There is no scientific debate,” Ricciardella said. “The debate is over.”

Autism is a developmental disability that typically appears during the first three years of life and affects a person’s ability to communicate and interact with others. Medical experts don’t have a comprehensive understanding of what causes autism, but they do know there is a strong hereditary component.

Thimerosal has been removed in recent years from most standard childhood vaccines.

Many members of the medical community are skeptical of the families’ claims. They worry that the claims about the dangers of vaccines could cause some people to forgo vaccines that prevent illness.

Ricciardella argued that a marketing consultant fanned publicity about the supposed link between thimerosal and autism in a journal called Medical Hypothesis. She described the journal as willing to publish radical ideas, so long as they are coherent. She also said the authors pay to have the article published.