A Trial To Evaluate A Multivalent Pneumococcal Conjugate Vaccine In Healthy Adults 50-85 Years Of Age

This is a 2-stage, phase 1/2, randomized, active-controlled, observer-blinded study with a 2-arm parallel design in each stage. In Stage 1 healthy adults 50 to 64 years of age with no history of pneumococcal vaccination will be randomized equally to receive either a single intramuscular dose of multivalent pneumococcal conjugate vaccine or a licensed tetanus, diphtheria, acellular pertussis combination vaccine (Tdap) (control group). In Stage 2 healthy adults 65 to 85 years of age previously vaccinated with Prevnar 13 \>=2 months prior to investigational product administration will be randomized equally to receive either a single intramuscular dose of multivalent pneumococcal conjugate vaccine or the licensed 23-valent pneumococcal polysaccharide vaccine (control group).