In less than two years, 4,000 suits have been filed against pharmaceutical companies over a mercury-laden preservative in childhood vaccines alleged to cause autism and other ailments.

Billions of dollars were at stake in what was shaping up to be one of the biggest litigation issues in history.

Then, without explanation, the suits were jeopardized because of a provision added to the domestic security bill signed Nov. 25 by President George W. Bush.

It protects Eli Lilly & Co. and other drug makers from suits, past and future, over the preservative thimerosal used widely in vaccines in the 1990s.

The White House has said it did not ask Congress to add the provision. No member of Congress will acknowledge proposing it. Lilly has denied asking for favors.

Parents here, like Michelle Mahnke, are fuming over the provision, which puts suits over thimerosal in a special "vaccine court."

Mahnke, 30, of Belleville, has a 5-year-old son, Jack, who has been diagnosed with autism. The child lives in a residential care facility where he is treated for the disorder.

Mahnke contends that thimerosal poisoned Jack, who was developing normally until around age 2 1/2, when his behavior turned dangerously violent.

Mahnke filed suit last week against a host of pharmaceutical companies, including Lilly.

"I was very angry that someone without a face was able to stop me from being able to recoup money from the responsible party," Mahnke said. "Someone needs to be held accountable."

She estimates that she has spent about $60,000 on her child's care.

"If my son can't get the treatment he needs, then this will end up being a burden on taxpayers," she said.

Rob Smith, a spokesman for Lilly, said his company contacted no one at the White House and had no direct involvement in the language of the bill.

"However, we have worked with members of Congress prior to that to get this clarification language inserted in the original homeland defense bill."

According to the provision, it affects "any vaccine set forth in the Vaccine Injury table, including any component or ingredient of any such vaccine." Smith contends that thimerosal is safe and that no study has ever shown a causal linkage between it and autism.

In Madison County, one law firm - Wise & Julian - has filed 17 thimerosal suits since April. A few have been filed in St. Louis in recent months, and more had been expected.

Wise & Julian, based in Alton, deals exclusively in mercury and asbestos cases. The company's Web site boasts that the firm has won $100 million in settlements in the last four years.

If such suits go to vaccine court, which awards payments from a consumer tax added to vaccinations, the damages for pain and suffering are limited to $250,000.

The new law had attorneys scrambling for countermoves last week.

"We are going to fight it," said Wise & Julian attorney Richard Saville, 38, of west St. Louis County. "We just haven't figured out how to do it yet."

Whether thimerosal, developed by Lilly in 1929, harmed children has been the subject of sharp debate.

Families coping with an explosion in autism that saw rates of the neurological disorder climb from 1 in 10,000 in the 1950s to current estimates of 1 in 500 viewed the preservative as the likeliest suspect.

While mercury is a known poison, scientific studies consistently concluded that there wasn't enough of it in vaccines to be harmful.

However, after conducting a review in 1999 of products containing mercury, the Food and Drug Administration issued a statement that infants who got thimerosal-laced vaccines might have been exposed to more mercury than recommended. The mercury has now been removed from most vaccines.

The most recent study, published last week in the British journal The Lancet, found that mercury levels in the blood of 33 children who got vaccines containing thimerosal were within federal safety limits.

Saville countered that the study did not test enough children and that its conclusions were flawed because they were based on how much mercury the subjects had excreted.

"The problem, at least in part for children who have been poisoned with mercury, is that they can't excrete it," Saville said.

The head of a consortium of personal injury law firms that have filed most of the thimerosal suits around the country said it was no mystery to him how the thimerosal provision got into the homeland security legislation.

Charles Siegel works for the Dallas firm of Waters & Kraus, which filed the first thimerosal suit in a state court in March 2001. His firm leads a national consortium, which includes Wise & Julian, that has filed similar cases in every major city, including St. Louis.

Siegel said the new law represents part of a concerted effort at national tort overhaul on the part of Republicans eager to reward corporations that donated heavily to the party in this year's elections.

"Thimerosal was the biggest (tort issue) to come along in a long time. It was right up there with asbestos and (the appetite suppressant) fen-phen," Siegel said, alluding to litigation that cost corporations hundreds of millions of dollars in settlements.

He noted that Lilly donated $1.6 million to candidates in the last election, 80 percent of it to Republicans.

He also discussed the close ties that Lilly has to the Bush administration: The elder George Bush was a Lilly board member in the 1970s, White House budget director Mitchell E. Daniels Jr. is a former Lilly executive, and the company's chief executive officer, Sidney Taurel, is on a council that advises Bush on homeland security.

"The Republicans are using their majority to curry favor with corporate interests," Siegel said. "It was payback time."

The White House declined to comment, referring questions to the Department for Homeland Security, which did not return phone calls last week and Monday.

Lilly is still a target

Wise & Julian filed mercury suits in Madison County on behalf of two children days after Bush signed the legislation.

The firm represented Michael and Kimberly Curia, who filed suit on behalf of their son, Christopher, as well as the Mahnkes.

The Mahnkes live in Belleville, and the Curias in Naperville, Ill., near Chicago.

Asked why the families declined to file in their home counties in favor of Madison County, which has a national reputation for being plaintiff-friendly, Saville would only say: "Venue statutes allow them to file here."

Siegel, the Dallas lawyer, said that barring a reversal of the law or a change in its language, most of the actual manufacturers of thimerosal named in the suits will, indeed, be off the hook. He said they included Bioport Corp., G.D.L. International, Parkdale Pharmaceuticals, Celltech Pharmaceuticals, Sigma-Aldrich Co., and Spectrum Chemical Manufacturing Corp.

But the lawyers still have Lilly in their sights.

"We are not suing Eli Lilly for manufacturing or adulterating. What we claim is that Eli Lilly was the original patenter, designer, defrauder and perverter of science," Siegel said. "That's a theory of liability not covered by the legislative amendments."

Reporter Paul Hampel: E-mail: phampel@post-dispatch.com Phone: 618-659-3639