Vaxcyte, Inc. announced on October 5, 2026, that its 31-valent pneumococcal conjugate vaccine candidate, VAX-31, met all prespecified primary endpoints in the OPUS-1 pivotal adult Phase 3 trial. The study evaluated the safety, tolerability, and immunogenicity of the VAX-31 High Dose formulation in healthy, pneumococcal-naïve adults in the United States. The trial enrolled 4,047 participants across approximately 30 sites, including a cohort of adults aged 50 and older (n=3,572) and a cohort of adults aged 18-49 (n=475).
In adults aged 50 and older, VAX-31 met all co-primary immunogenicity endpoints compared to the comparators Prevnar 20 (PCV20) and Capvaxive (PCV21). Specifically, all 28 serotypes shared with PCV20 and/or PCV21 met the noninferiority criterion (lower bound of the 95% confidence interval >0.667). Additionally, the three serotypes unique to VAX-31 and the cross-reactive serotype 20B met the superiority criterion (lower bound >2.0). For the prespecified primary immunobridging endpoint, VAX-31 met the noninferiority criterion for all 32 serotype comparisons in adults aged 18-49 compared to adults aged 50-64.
Regarding safety, VAX-31 was well tolerated and demonstrated a safety profile similar to PCV20 and PCV21 across all ages studied. Solicited local and systemic reactions were generally mild-to-moderate and resolved within 48 hours. No serious adverse events were considered related to the study vaccines, and there were no study discontinuations due to adverse events.
The company stated that these results serve as the cornerstone for a planned filing of a Biologics License Application (BLA) with the U.S. Food and Drug Administration. Vaxcyte anticipates reporting results from the OPUS-2 and OPUS-3 adult Phase 3 trials in the first half of 2027. The company also noted that the FDA expanded the Breakthrough Therapy designation for VAX-31 in May 2025 to include the prevention of pneumonia caused by Streptococcus pneumoniae in adults.
