This study aims to test a new vaccine for infants to see if it's safe and helps protect against infections like pneumonia (lung infection), meningitis (brain infection), and otitis media (ear infection). These are caused by a germ called Streptococcus pneumoniae. Two groups of babies, about 2 months old, will get either the new vaccine, PG4, or the existing one, 20vPnC (Prevnar 20®). Each group will receive shots at 2, 4, 6, and 12-15 months of age. The study lasts for 16-19 months, and involves 6 clinic visits and 1 phone call. Parents will be asked if their baby has any side effects, which are unexpected reactions to the vaccine.

• Duration: 16-19 months, with 6 visits and 1 phone call
• Eligibility: Healthy infants around 2 months old
• Risks: Possible side effects from the vaccine