Families claiming that a mercury-based preservative in vaccines triggers autism will challenge mainstream medicine in federal court today, seeking vindication and financial redress from a government fund that helps people injured by shots, the Associated Press writes.

Two 10-year-old boys from Portland, Oregon, will serve as test cases that determine whether the children and their families in similar situations should be compensated. Attorneys for the boys will attempt to show the boys were happy, healthy and developing normally, but after being exposed to vaccines with thimerosal, they began to regress and show symptoms of autism, the AP reports.

Thimerosal has been removed in recent years from standard childhood vaccines, except flu vaccines that are not packaged in single-doses. The CDC says single-dose flu shots currently are available only in limited quantities. In 2004, a committee with the Institute of Medicine concluded there was no credible evidence that vaccines containing thimerosal caused autism, the AP reminds us.

Overall, more than 4,800 families have filed claims with the US Court of Claims alleging that vaccines caused autism and other neurological problems in their children. Lawyers for the families will present three different theories of how vaccines caused autism.

The Office of Special Masters of the claims court has instructed the plaintiffs to designate three test cases for each of the three theories - nine cases in all - and has assigned three special masters to handle the cases. Three cases in the first category were heard last year, but no decisions have been reached.

The two cases beginning today are among the three focusing on the second theory: that thimerosal-containing vaccines alone cause autism. The plaintiff in the third case originally scheduled for hearing this month has withdrawn and lawyers and court officials are working to agree on substitute case, the AP writes. Hearings in test cases for the third causation theory are scheduled in mid-September.

Lawyers for the petitioning families in the cases being heard this month say they will present evidence that injections with thimerosal deposit a form of mercury in the brain. That mercury excites certain brain cells that stay chronically activated trying to get rid of the intrusion. “In some kids, there’s enough of it that it sets off this chronic neuroinflammatory pattern that can lead to regressive autism,” says attorney Mike Williams.

In the end, the families and their attorneys hope to convince the special master hearing their case that thimerosal belongs on the list of causes for the inflammation that leads to regressive autism. To win, the attorneys for the two boys, William Mead and Jordan King, will have to show that it’s more likely than not that the vaccine actually caused the injury.

Arguments are scheduled to go on throughout the month and a final decision could take several more months, the AP writes, adding that successful claims would result in compensation taking into account lost earnings after age 18 and up to $250,000 for pain and suffering. The families or the federal government can also appeal a decision to the Court of Federal Claims or to a federal appeals court.

The court’s web site says more than 12,500 claims have been filed since creation of the program in 1987, including more than 5,300 autism cases, and that more than $1.7 billion has been paid in claims. It says there is now more than $2.7 billion a trust fund supported by an excise tax on each dose of vaccine covered by the program.