The objectives of this Phase I/II study are to assess the safety and immunogenicity of two different dose levels of a non-adjuvanted H5N1 influenza vaccine in a healthy young adult population. Subjects will be randomized 1:1 to receive two intramuscular injections (21 days apart) of the vaccine containing either 3.75 µg or 7.5 µg H5N1 hemagglutinin (HA) antigen in a non-adjuvanted formulation. Subjects will be monitored for safety and for antibody response to the vaccine. A data safety monitoring board will review the safety data after the first and second vaccination.