Protein Sciences Corp. may be one step closer to approval of what would be the first cell culture-derived flu vaccine after an FDA advisory committee voted last week in favor of its use in adults ages 18-49. However, the panel concluded the available data were not yet sufficient to support the safety of FluBlok in people ages 50 and up, not because of doubts about the novel manufacturing technology, but rather because of a few rare events, combined with a small safety database.

There are five trivalent inactivated influenza vaccines approved for use in the U.S. A sixth approved vaccine, FluMist from AstraZeneca plc's MedImmune LLC unit, is a live attenuated vaccine. All are manufactured using hen eggs.