This study aims to test a new vaccine for babies against germs causing pneumonia (lung infection), meningitis (brain infection), and otitis media (ear infection). Pneumococcal disease is an illness caused by a germ called Streptococcus pneumoniae. The new vaccine is compared to the current one, 20vPnC (Prevnar 20®). Babies will be divided into three groups. In each group, babies will get shots either of the new vaccine or the current one, with some getting it in the muscle and others under the skin.

• Duration: Babies will be in the study for 12 to 21 months, depending on the group.
• Visits: Each baby will have 6 clinic visits and 1 phone call during the study.
• Side Effects: Parents will report any unexpected reactions to the vaccine.

Blood samples will be taken to see how well the vaccine works. Babies must be healthy and between 2 to 6 months old to join. Those with severe allergies or past reactions to vaccines cannot participate.