Abstract: Compositions and methods are provided for reducing the mammalian transmission of Streptococcus pneumoniae (S. pneumoniae) through the administration to mammalian subjects of vaccine compositions comprising at least one immunogenic polypeptide comprising a S. pneumoniae protein or a fragment or variant thereof that is required for or involved in transmission of the bacteria between mammalian hosts. These vaccine compositions also serve to reduce the incidence rate of at least one invasive disease caused by S. pneumoniae. Methods are also provided for identifying additional genetic factors involved in mammalian transmission of S. pneumoniae.