The purpose of this study is to evaluate a study vaccine called 20-valent pneumococcal conjugate vaccine (20vPnC). The study will assess whether the study vaccine is safe to use in healthy infants. It will also evaluate if the study vaccine can help the body make antibodies (known as immune response). These antibodies help protect against 20 types of pneumococcal bacteria. The study will compare 20vPnC with 13vPnC (control vaccine), which is approved for use in infants.
The study is seeking participants who:
* Are healthy infants
* Aged 42 to 98 days of age at the time of consent.
Infants will receive either 20vPnC or 13vPnC. Doses will be given at approximately 2, 4, and 6 months of age (Doses 1 through 3). A fourth dose will be given at 12 to 15 months of age. Infants will receive the same vaccine (20vPnC or 13vPnC) for all 4 doses.
The total time of the study will be about 16 to 19 months. A subset of infants will be asked to stay in the study for longer.