There is evidence that aluminum phosphate (AlPO4) contained as an adjuvant in conjugate vaccines enhances the immune response in infants. There is no data so far evaluating whether this also applies to adults. The objective of this study is to compare the immune response of 2 different 13-valent pneumococcal conjugate (13vPnC) formulations with and without AlPO4 to select a formulation and to compare the immune response to the chosen 13vPnC formulation relative to the immune response to 23-valent pneumococcal polysaccharide vaccine (23vPS).

Inclusion Criteria:

• Male and female adults 65 years of age and older.
• Determined by medical history, physical examination, and clinical judgment to be eligible for the study.
• Expected to be available for the duration of the trial (up to approximately 13 months).

Exclusion Criteria:

• Received previous immunization with 23vPS.
• Serious chronic disorders including metastatic malignancy
• Known or suspected hypersensitivity to any vaccine or vaccine components