The Supreme Court is trying to sort out whether drug companies can be sued for claims of serious side effects from childhood vaccines without driving vaccine makers from the market and risking a public health crisis.

The court heard argument Tuesday in an appeal filed by Pittsburgh area parents who want to sue Pfizer Inc.'s Wyeth for the serious health problems they say their 18-year-old daughter suffered from a vaccine she received in infancy.

Several justices appeared sympathetic to the parents' claims.

Wyeth, backed by the Obama administration and many public health groups, argued that Congress shielded drug companies from most vaccine lawsuits when it created a special vaccine court 24 years ago to handle the claims.