Immunogenic influenza hemagglutinin-derived peptide compositions described herein induce a specific therapeutic antibody response against influenza virus. The immunogenic peptide compositions comprise a segment from the fusion initiation region (FIR) domain of an influenza hemagglutinin protein bound to an immunogenic carrier protein, such as an influenza hemagglutinin (HA) protein (i.e., full length HA), and the like. The immunogenic peptide compositions described herein can be utilized to treat or prevent influenza infection and to prepare influenza-specific therapeutic antibodies that interfere with influenza virus-host cell membrane fusion. The peptide conjugates can be formulated in pharmaceutical compositions useful for broad spectrum treatment or prevention of influenza infections.