Saint Louis University is seeking volunteers for a study on a vaccine against smallpox as a bioterrorist agent.

The university's Center for Vaccine Development is leading the National Institutes of Health-funded study at five U.S. centers.

The world was declared free of the highly contagious and potentially lethal smallpox in 1980. But the use of smallpox as a form of bioterrorism is cause for concern, and the U.S. government wants to protect citizens in the event of an attack.

The study will compare two smallpox vaccines and the body's immune response when the vaccine is administered two different ways.

Nearly 250 volunteers are needed for studies in St. Louis, Iowa, Maryland, Atlanta and Seattle.