VAX-31 Shows Superior Immune Response to Rival Vaccine
Vaxcyte has solidified its position as a contender in the pneumococcal vaccine market with the March 18 publication of positive Phase 1/2 trial data for its VAX-31 candidate in The Lancet Infectious Diseases. The study, which enrolled 1,015 healthy adults aged 50 and older, directly compared VAX-31 against the current standard-of-care, Prevnar 20® (PCV20). Results showed VAX-31 was well-tolerated, demonstrating a safety profile similar to PCV20 over a six-month evaluation period.
The key differentiator emerged in the vaccine's immune response. VAX-31, a 31-valent candidate, met or exceeded non-inferiority criteria for all 20 serotypes it shares with PCV20. Crucially, it met the superiority criteria for the 11 incremental serotypes unique to VAX-31. The Vaxcyte candidate generated greater average immune responses for 18 of the 20 shared serotypes, with seven of those achieving a statistically higher response than Prevnar 20®.
Vaccine Aims for 95% Disease Coverage in Phase 3 Trial
These clinical results translate into a significant strategic advantage. VAX-31 is designed to provide coverage against approximately 95% of invasive pneumococcal disease (IPD) and 88% of pneumococcal pneumonia in U.S. adults over 50. This represents a potential incremental 14-34% broader coverage for IPD and 19-31% for pneumonia compared to existing vaccines, addressing a major unmet need in a market where antibiotic resistance is a growing threat.
Buoyed by the data, Vaxcyte has advanced the VAX-31 high-dose formulation into its OPUS Phase 3 program. The trial's success would support a Biologics License Application and could fundamentally reshape the competitive landscape. Investors are now looking toward the next major catalyst, with topline data from the pivotal OPUS-1 non-inferiority trial expected in the fourth quarter of 2026.
Based on the strength of the unprecedented results from this study, we advanced VAX-31 into a comprehensive Phase 3 adult program and believe we are uniquely positioned to set a new standard by which future adult pneumococcal vaccines will be measured.
— Grant Pickering, Chief Executive Officer and Co-Founder of Vaxcyte.
Edgen Stock·Mar 19 2026, 00:07
