An polyvalent vaccine used to prevent infection by the bacterium Streptococcus pneumoniae. Pneumococcal polyvalent vaccine contains higly purified capsular antigens from the 23 most prevalent or invasive pneumococcal types of Streptococcus pneumoniae to ensure cross-protection. Following vaccination, protective capsular type-specific antibody levels typically develop by the third week; serotype-specific antibody levels generally decline after 5-10 years.