Researchers have identified a group of antibodies that neutralize a wide range of influenza viruses, including the H5N1 avian influenza, the 1918 Spanish flu and some seasonal strains. These molecules may one day be used therapeutically to protect patients against a broad array of strains. The antibodies also give researchers clues about how to develop new vaccines. "This opens up the avenue of thinking about universal influenza vaccines, which has not been realistic before," says Peter Palese, an influenza expert at Mount Sinai School of Medicine in New York who was not involved in the work.