Vaxcyte Advances High-Dose VAX-31 to Phase 3 After 31-Serotype Data Showing 95% IPD Coverage
Vaxcyte’s Phase 1/2 adult study of its 31-valent VAX-31 vaccine demonstrated robust opsonophagocytic activity and IgG responses across all 31 serotypes, meeting noninferiority for 20 common serotypes and superiority for 11 incremental serotypes versus Prevnar 20. The high-dose formulation, covering approximately 95% of invasive pneumococcal disease and 88% of pneumonia in U.S. adults aged 50+, has advanced into a comprehensive Phase 3 OPUS program with topline data expected in Q4 2026.
1. Phase 1/2 Study Results
The VAX-31 Phase 1/2 trial enrolled 1,015 healthy adults aged 50 and older in a randomized, observer-blind, dose-finding design comparing three dose levels to PCV20, and demonstrated robust opsonophagocytic and IgG responses across all 31 serotypes at every dose.
2. Immunogenicity and Serotype Coverage
The high-dose cohort met noninferiority criteria for the 20 shared serotypes with Prevnar 20 and exceeded superiority thresholds for all 11 additional serotypes unique to VAX-31, achieving a geometric mean ratio above 1.0 for 18 of 20 common serotypes and promising coverage of ~95% of invasive disease and ~88% of pneumonia serotypes in adults.
3. Safety and Tolerability
VAX-31 exhibited a safety profile comparable to PCV20, with predominantly mild-to-moderate local and systemic reactions that resolved within days and no serious adverse events attributed to the vaccine.
4. OPUS Phase 3 Program
Based on the unprecedented Phase 1/2 results, Vaxcyte advanced the high-dose VAX-31 into its comprehensive OPUS Phase 3 adult program, featuring head-to-head noninferiority trials versus PCV20 and PCV21, with topline data slated for Q4 2026 to support a Biologics License Application.