A provision added to the Homeland Security Act just days before Congress approved the legislation last month restricts families from filing lawsuits against the maker of Thimerosal, a mercury-based vaccine preservative linked to the development of autism. Instead, before they can take their claims to civil court, families are now required to file claims under the National Vaccine Injury Compensation Program, which limits damages for pain, suffering and death to $250,000. In addition, the Justice Department has filed a request to restrict in subsequent civil court cases the use of any information gathered or revealed during a compensation program proceeding.

Thimerosal, which was made by pharmaceutical manufacturer Eli Lilly and Co. until the 1980s, is 50 percent mercury and may be responsible for exposing some children to mercury levels significantly higher than Federal guidelines recommend.