Safety and Efficacy of wSp Vaccine in Young Children

Inclusion Criteria: 1. Male or female who is 6 months (+/- 30 days) of age at time of enrollment 2. Healthy subject as established by medical history and clinical examination before entering into the study. 3. Received 3 doses of PCV-20. 4. Written informed consent obtained from the subject's parent/legal guardian. 5. Parent/legal guardian able and willing to bring subject to all study visits. Exclusion Criteria: 1. Has a history of invasive pneumococcal disease (positive blood culture and/or positive cerebrospinal fluid culture). 2. Known or suspected impairment of immunological function, based on medical history and physical examination. 3. Has a history of congenital or acquired immunodeficiency. 4. Chronic administration (defined \> 14 consecutive days) of immunosuppressants or other immune-modifying drugs, or during the study period. 5. Prior receipt since birth of immunoglobulins and/or any blood products or planned administration during the study period. 6. Expected to receive systemic corticosteroids within 14 days prior to any dose of study vaccine. 7. External auditory canal atresia/stenosis. 8. Has known or history of functional or anatomic asplenia. 9. Has a bleeding disorder in which intramuscular vaccination would be contraindicated. 10. Participation in another investigational or interventional trial within the 28-day period before enrollment and during the conduct of the study. Participation in observational studies is permitted. 11. Direct descendant (child or grandchild) of study site personnel. Temporary exclusion criteria For day of vaccination: 12. Fever (transcutaneous temperature ≥38.0°C) or acute illness 13. Has received systemic corticosteroids (equivalent of prednisone \> 0.5 mg/kg/day or equivalent) and not completed this course of treatment at least 30 days prior to the study vaccination. Inhaled, topical, and ophthalmic steroids are allowed.