During an hour-long oral argument Tuesday, several justices said they worried that allowing lawsuits against vaccine makers could force some manufacturers to leave the market, thus undermining the nation's vaccine supply.
Justice Anthony Kennedy, often a key vote on the court, said defending against product-liability lawsuits is a "tremendous expense," adding that drug makers may face pressure to settle cases even if they were likely to win them on the merits.
Other justices, however, expressed concern that if federal law preempted lawsuits against vaccine makers, those manufacturers would not have much incentive to keep testing their products or look for alternatives that may prove to be safer.
Justice Sonia Sotomayor was particularly vocal in questioning whether vaccine makers would have a motivation to look for safer vaccines if they faced no threat from lawsuits.
At issue in Tuesday's case was a Pennsylvania family's argument that it should be able to sue Pfizer Inc.'s (PFE) Wyeth unit on allegations that the drug maker could have marketed a safer vaccine but chose not to do so.
The Pennsylvania parents alleged their daughter, Hannah Bruesewitz, developed residual seizure disorder after receiving a diphtheria, tetanus and pertussis vaccine manufactured by Wyeth when she was six months old.
The parents said their daughter, now a teenager, has profound developmental impairments and will need care for the rest of her life. They filed a petition for compensation under a special vaccine program administered through the U.S. Court of Federal Claims, but that claim was rejected. The family then filed a lawsuit in state court.
A U.S. appeals court ruled last year that the lawsuit was preempted by the National Childhood Vaccine Injury Act of 1986. That law that created the national compensation program for vaccine-injury claims, but it also gave vaccine makers protection from some lawsuits.
The law said a manufacturer could not be sued if a vaccine-related injury resulted from side effects that were unavoidable even if the vaccine was made properly and accompanied by proper directions and warnings.
A key question in the case is what Congress meant by unavoidable side effects. Several justices said the law was unclear.
David Frederick, a lawyer for the plaintiffs, said Bruesewitz's injuries could have been prevented. He argued that a ruling for Wyeth would mean that vaccine makers were protected from lawsuits even when they knew a safer vaccine design was available.
Wyeth has denied that its vaccine caused the child's injuries. Kathleen Sullivan, a lawyer for the company, said Congress meant the 1986 law to protect vaccine makers from a wave of lawsuits that threatened their businesses. If the high court rules for the plaintiffs, "there will be enough liability to drive manufacturers from the market," she said.
The Obama administration is supporting Wyeth in the case. A Justice Department lawyer argued Tuesday that Congress intended for socially beneficial vaccines to be on the market even if they had side effects. Lawsuits ought not be a driving force to push vaccines off the market, he said.
Tuesday's argument appeared too close to call. Justice Elena Kagan is recused in the case because she participated in it while serving as U.S. solicitor general. If the remaining eight justices were to split 4-4, the lower court ruling for Wyeth would be affirmed but no precedent would be set by the case.
A ruling is expected by the end of June.