A Phase 2 Study to Evaluate the Safety, Tolerability, and Immune Response of AFX3772 Vaccine in Healthy Infants

This is a Phase 2 clinical study to support the use of AFX3772 in healthy infants for the prevention of pneumococcal disease. The purpose of this study is to determine the safety, tolerability, and immunogenicity of 3 different formulations of AFX3772 compared with Prevnar 13 (PCV13) and Prevnar 20 (PCV). Infants approximately 2 months of age will be enrolled and receive 4 doses of study vaccine over 8 protocol-defined visits spanning a duration of approximately 18 to 21 months. Part 1 is the dose escalation, lead-in portion of the study in which infants at each dose level will be randomized 3:1 in sequential cohorts of increasing doses of AFX3772 or PCV13. Enrollment in Cohorts 2 and 3 will proceed following Data Monitoring Committee (DMC) review of cumulative safety and tolerability data from preceding cohorts. Following completion of DMC review of safety and tolerability data for the cohorts enrolled in Part 1, additional infants will be enrolled and randomized equally to receive either PCV20 or AFX3772 at different dose levels approved for evaluation in Part 2.