ATLANTA --- The Georgia Supreme Court allowed an Atlanta couple's lawsuit against a vaccine manufacturer to go forward, upholding a first-of-its-kind ruling by an appellate court that had drawn fierce opposition from the vaccine industry.

The court's unanimous decision Monday concluded that a 1986 federal law that has been used to block other suits against vaccine companies does not bar the suit from Marcelo and Carolyn Ferrari from going to trial.

It upheld a ruling by the Georgia Court of Appeals, which became the first appellate court in the nation to hold that the National Childhood Vaccine Injury Compensation Act does not pre-empt state law.

The Ferrari family asked the Georgia Supreme Court to rule that vaccine maker American Home Products Corp., now known as Wyeth, can be held liable for damages in a civil case involving their son, Stefan.

The family believes they can prove that thimerosal, the mercury-based preservative, caused their son's disability. Stefan, they say, was a talkative toddler before he got a round of boosters shots when he was 18 months old. The boy, now 10, hasn't spoken since.

The case has drawn protests from the vaccine industry and powerful lobbying groups from the U.S. Chamber of Commerce to the conservative Pacific Legal Foundation.

Seven other state courts have ruled that the federal laws pre-empt any state law that might give families the power to challenge the vaccine manufacturers.

But the Georgia Court of Appeals became the first appellate court in the nation to rule that the federal law doesn't take precedence over state tort rules, calling the federal statute unclear.

At hearings in May, attorneys for the Madison, N.J.-based company argued that other judges have concluded Congress wanted the federal law to pre-empt state rules, in part so that manufacturers aren't subjected to a mishmash of different state standards.

Wyeth spokesman Doug Petkus said the company would appeal Monday's decision to the U.S. Supreme Court. He said other courts have agreed that the federal law supersedes state claims for injuries if the vaccines are prepared with FDA-approved designs and are accompanied by the proper warnings.

The Ferraris' attorney, Lanny Bridgers, contended that the federal law was meant to supplement, not displace, state law.

The Georgia Supreme Court's ruling, written by Justice George Carley, said the federal law "does not pre-empt all design defect claims against vaccine manufacturers."

Instead, the court held, vaccine manufacturers must prove on a case-by-case basis that the side effect of the particular vaccine were unavoidable to be immune from defective design claims.

Families have claimed in court that thimerosal is linked to autism, although government lawyers say the Centers for Disease Control and Prevention has rejected any link.