Polypeptide epitopes are defined herein which when used as components of vaccine compositions, induced partial immunity to Schistosoma mansoni. The epitopes are found on the surface of schistosumula. The epitopes are part of larger proteins which are immunologically cross-reactive with myosin heavy chains from other species. However, anti-myosin antibodies directed against myosin molecules of other species are not cross-reactive with the surface epitopes of S. mansoni.