Vaxcyte (PCVX) Study Result summary

Study design and population

• Phase 1/2 randomized, observer-blind, dose-finding study evaluated VAX-31 in 1,015 healthy adults aged 50 and older, comparing three VAX-31 doses to PCV20.

• Subjects were monitored for safety and immunogenicity at multiple timepoints up to six months.

• Demographics were well balanced across cohorts, with high retention and over 96% completing immunogenicity follow-up.

Safety and tolerability

• VAX-31 demonstrated a safety profile similar to PCV20 across all doses, with most local and systemic reactions mild to moderate and self-resolving.

• Incidence of unsolicited adverse events, medically attended events, new chronic illnesses, and serious adverse events was low and comparable between VAX-31 and PCV20.

• No related serious adverse events were observed; reported SAEs were typical for the age group and balanced across arms.

• No clustering of adverse events or unexpected safety signals were detected.

Immunogenicity and efficacy findings

• VAX-31 induced robust opsonophagocytic activity (OPA) immune responses for all 31 serotypes at all doses.

• High and middle doses met or exceeded regulatory OPA criteria for all 31 serotypes; low dose met criteria for 29.

• For the 20 serotypes shared with PCV20, most geometric mean ratios (GMRs) were greater than PCV20; high dose showed GMR >1.0 for 18 serotypes and statistical superiority for 7.

• All three doses met superiority criteria for the 11 incremental serotypes, with dose-dependent increases in antibody titers.

• IgG data were consistent with OPA results, confirming robust immune responses.