Study Evaluating a 13-valent Pneumococcal Conjugate Vaccine in Elderly Subjects

This is a follow-up study to the core study NCT00269672 (6115A1-500). This study will further evaluate the safety, tolerability, and immunogenicity of 13-valent pneumococcal conjugate vaccine (13vPnC) when administered to subjects who have already received one dose of 13vPnC, and one dose of 23-valent pneumococcal polysaccharide vaccine (23vPS) one year later. This study will determine if a subsequent dose of 13vPnC one year later results in similar or greater immune response (body's ability to protect against disease) than that measured after the initial dose of 13vPnC.