New report to address possible link between vaccines and autism.

Byline: John A. MacDonald

WASHINGTON _ Lyn Redwood's son Will was a happy baby who "ate, slept well, smiled, cooed, walked and talked, all by one year," his mother recalls.

But shortly after his first birthday, Will unexpectedly developed several infections, stopped talking, lost eye contact and suffered intermittent bouts of diarrhea. He ultimately was diagnosed as having a form of autism, a severe neurological disorder.

A couple of years later, his mother read a report that said children who received vaccines containing thimerosal, a mercury-based preservative, could have been exposed to more mercury than federal guidelines recommend. Since then, Redwood has been convinced that the vaccines Will received five years ago led to his autism, and that the federal government is ignoring the vaccine-autism issue.

Thousands of parents share Redwood's belief, while most of the nation's medical establishment says there is no scientific basis to believe that vaccines are responsible for autism. After a lengthy investigation, the Institute of Medicine, an arm of the highly regarded National Academy of Sciences, will issue a report Tuesday that will attempt to answer an increasingly contentious question: Is there a connection between vaccines and autism?

The report takes on special significance because the number of parents refusing to have their children follow traditional vaccination schedules is on the rise. Many think the trend has been fueled by news stories, Internet sites and word-of-mouth reports of adverse effects from vaccines, the American Medical Association said.

Meanwhile, the prevalence of…