Federal health officials have concluded that childhood vaccines contributed to symptoms of the disorder in a 9-year-old Georgia girl, Hannah Poling. An investigation by the U.S. Department of Health and Human Services has concluded that her family is entitled to compensation from a federal vaccine injury fund, The Atlanta Journal-Constitution reports.

"It's a beginning," said Kevin Conway, a lawyer representing more than 1,200 families with vaccine injury claims, to AP. "Each case is going to have to be proved on its individual merits. But it shows to me that the government has conceded that it's biologically plausible for a vaccine to cause these injuries. They've never done it before."

Hannah is the daughter of a neurologist, Dr. Jon Poling.

A leaked document posted online details how the government's Division of Vaccine Injury Compensation concluded that five shots Hannah received in 2000, when she was 19 months old, "significantly aggravated an underlying mitochondrial disorder" and resulted in a brain disorder "with features of autism spectrum disorder." The actual vaccine-court document was kept sealed by the court.

Following the leak, many groups have called for access to the documents so the link between vaccines and autism can be fully evaluated. At the core of the debate is thimerosal. The rise in autism cases is not yet explained, but large-scale studies have shown there is no link to the mercury-containing preservative found in some vaccines.

However, some parents such as Hannah's allege that only when many shots are given at a time its neurological adverse effects, such as autism spectrum disorders, can be seen. "HRSA has maintained and continues to maintain the position that vaccines do not cause autism," the government said.

Rates of children suffering from autism in California have risen despite the removal of the preservative thimerosal from childhood vaccines in 2001, researchers said in a study published in January in the Archives of General Psychiatry, a publication of the Journal of the American Medical Association. Researchers analyzed autism rates in young children over a 12-year period and discovered the first hard evidence that thimerosal plays no role in autism.  

It seems that removing thimerosal from all recommended infant vaccines as a precautionary measure in March 2001 had no effect on reducing the number of children suffering from autism. The only childhood vaccines that contain more than trace amounts of thimerosal are multiple-dose vials of some flu vaccines.

A previous look on data referring of thimerosal affecting children from 2001 suggested there was a decline in autism beginning with 1994. The new data from March 2007 did not reflect such decline. Researchers from the California Department of Public Health studied the prevalence of children with autism in California from 1995 through 2007. They discovered that the rate of all developmental disabilities increased from 504 to 905 per 1,000 live births.

Researchers believe that "there is an environmental source" linked to increased rates of autism.