The United State Court of Federal Claims began another hearing on Monday to decide whether vaccines containing a toxic preservative known as thimerosal should be responsible for autism in thousands of children who received the vaccines, The New York Times reports. The results of the hearing are not expected until next year.

This hearing was said to be the second in a series of three in which the court is considering whether the government should pay millions to the families of some 4,800 autistic children. Parents in the case are claiming that thimerosal damaged their children's brains leading to development of autism. The toxic preservative was removed from pediatric vaccines starting in 2001. Now in some pediatric vaccines if not all, another toxic preservative, an aluminum compound, is used.

Early studies have showed that vaccines with thimerosal were not linked to increased risk of autism in children although parents, critics and some scientists suspected that the increase incidence of autism in the U.S. has something to do with thimerosal-containing vaccines.

Autism was rare a couple of decades ago. Now one in every 150 children suffer this disease, according to the Center for Disease Control and Prevention, the U.S. health agency that promotes use of vaccines.

Parents whose children are injured by pediatric vaccines recommended by the government have no right to filing suits against vaccine makers, doctors and hospitals. The only compensation for the injury if proved to be caused by the vaccines will have to be granted by the Federal Claim court through a legal proceeding.

One similar vaccine-autism case reported not long ago involved Hannah Poling, an autistic 9-year old girl from Athens, GA, according to the times. Poling grew normally until a vaccine was administered. The U.S. government conceded that the vaccine she received boosted a mitochondrial dysfunction in the girl, ultimately leading to autism. The family was granted an unknown amount of compensation.

Critics said, according to the times, the government concession is strong evidence that vaccine causes autism, but the government said that the Poling case should not be considered as a precedent for later cases. Findings by some studies showed mitochondrial dysfunction was fairly common among autistic children, suggesting that vaccines may have an impact on children through this dysfunction.

The current case, presented by a lawyer named Thomas Powers, involved mainly two 10 yea-old boys from Portland Oregon, William Mead and Jordan King, who grew normally until after they were vaccinated. But the hearing is not expected to result in any conclusion until next year.

At least one study released not long ago showed that the incidence of autism is not on the decline even though thimerosal has not been used since 2001 in pediatric vaccines. Some organizations interpreted the observation as evidence that disproves the association between thimerosal and increased risk of autism. But this study in itself could not prove that thimerosal was not responsible for the increased risk of autism.