( CNN ) -- As flu season rages across the United States , federal regulators say they have approved a new kind of vaccine for the virus . The new product , Flublok , which is available in limited supplies for the current season , is different from other flu vaccines , because it is n't made using eggs or an influenza virus , the Food and Drug Administration said Wednesday . Instead , Flublok 's production involves programming insect cells grown in steel tanks to produce large amounts of a particular flu virus protein , known as hemagglutinin , according to Protein Sciences , the vaccine 's manufacturer . Most human antibodies that fight flu infection are directed against hemagglutinin , the FDA said . Flu vaccine attitudes abroad differ from U.S . This method allows for more rapid production , making more of the vaccine available more quickly in the event of a pandemic , the FDA said . `` This approval represents a technological advance in the manufacturing of an influenza vaccine , '' said Karen Midthun , director of the FDA 's Center for Biologics Evaluation and Research . It has already been used in vaccines approved for other infectious diseases . Flublok is approved only for adults ages 18 - 49 . Flu activity is `` elevated '' in most of the United States , Dr. Thomas Frieden , director of the Centers for Disease Control and Prevention , said last week . Manufacturers said there was plenty of vaccine for those who want to get a flu shot . But there have been reports of spot shortages , Frieden said . Flublok will be available in limited supply this winter and widely available during the next flu season , said Protein Sciences , which is based in Meriden , Connecticut . Flublok contains the elements necessary to help fend off three different flu strains , including H1N1 and H3N2 , the regulator said . And it proved 44.6 % effective against all influenza strains in circulation , not just those that matched the strains included in the vaccine , according to the FDA . Flu vaccine poses no risk to unborn .
Unlike other flu vaccines , Flublok does n't rely on bacteria or the flu virus . Instead , it 's made by growing a virus protein in insect cells . This allows for more rapid production in the event of a pandemic , the FDA says . The vaccine is available in limited supplies during the current flu season .