Around 5,000 families who believe that a mercury-based preservative, thimerosal, found in many vaccines causes the development of autism have filed claims with the U.S. Court of Claims. The families allege vaccines caused autism and other neurological problems in their children.

Autism is a developmental disability which usually appears in children during their first 36 months. Once an uncommon disorder in the United States, the incidence of autism is now occurring at epidemic rates.

The case, which began Monday, offers two 10-year-old boys from Portland, Oregon, William Mead and Jordan King as test cases for the theory that thimerosal-containing vaccines cause autism.

They will show the federal court that the two boys were developing normally until they were exposed to vaccines with the mercury-based preservative, thimerosal, a preservative containing mercury.

In 2007, three test cases were presented in court to examine whether the combination of measles-mumps-rubella (MMR) vaccines containing thimerosal cause autism. Four more test cases this year to determine whether MMR vaccines, regardless of whether or not they contain thimerosal, may bring about the condition.

Arguments in favor of vaccine safety tend to emphasize that no connection has been proven, and that vaccines are such an overwhelming public good that even raising the possibility of not vaccinating children is irresponsible.

The Vaccine Education Center at the Children's Hospital of Philadelphia disputes evidence claiming to link MMR to autism, supports evidence of a genetic connection, and concludes that "unfortunately, for current and future parents of children with autism, the controversy surrounding vaccines has caused attention and resources to focus away from a number of promising leads."

Many pharmaceutical companies have begun the process of taking thimerosal out of their vaccines intended for children. If successful, the families could receive compensation up to $250,000 for past and future medical expenses, special education expenses and other problems.