Novel vaccines for use against .beta.-hemolytic Streptococcus colonization or infection are disclosed. The vaccines contain an immunogenic amount of a variant of streptococcal C5a peptidase (SCP). Also disclosed is a method of protecting a susceptible mammal against .beta.-hemolytic Streptococcus colonization or infection by administering such a vaccine. Enzymatically inactive SCP, and polynucleotides encoding these SCP proteins are further disclosed.