The Food and Drug Administration gave its approval to FluMist, a nasal spray flu vaccine developed by MedImmune ( MEDI) that's designed to serve as an alternative to flu shots. FluMist can be used for people ages 5 to 49. It's the first live-virus influenza vaccine approved in the U.S. According to the Centers for Disease Control and Prevention the flu is responsible for about 36,000 deaths each year in the U.S. Each dose of FluMist will contain the three virus strains recommended by the U.S. Public Health Service for the 2003-04 flu season -- two strains of influenza A, which causes the most severe and widespread outbreaks, and one strain of B which usually causes a milder illness. Unlike the circulating strains, the live viruses in the vaccine are modified so that they don't grow well at human body temperature but do replicate enough to induce protective immunity, the FDA said in a statement. MedImmune, based in Gaithersburg, Md., will market FluMist with Wyeth ( WYE). Shares of MedImmune were down 41 cents, or 1%, to $39.32 recently. Wyeth was up $2.25, or 4.7%, to $49.69.