The purpose of this study were to obtain additional evidence in support of the safety and immunogenicity of a recombinant hemagglutinin (rHA) vaccine in an elderly population, and to establish non-inferiority of the immunogenicity of the rHA vaccine when compared with a licensed trivalent influenza vaccine (TIV). Another purpose was to provide a preliminary estimate of the relative efficacy of the two vaccines against culture-positive influenza-like illness during the subsequent epidemic.