Vaxcyte's VAX-31 meets all primary endpoints in OPUS-1 Phase 3, supporting BLA plan

What's the story? On 5 October 2026 Vaxcyte reported positive topline results from OPUS-1, the pivotal adult Phase 3 trial of VAX-31, its 31-valent pneumococcal conjugate vaccine candidate. VAX-31 met all prespecified primary endpoints across the age groups studied against Pfizer's Prevnar 20 (PCV20) and Merck & Co.'s Capvaxive (PCV21). In adults aged 50 and older, all 28 serotypes shared with the comparators met the non-inferiority criterion, while all three serotypes unique to VAX-31 plus cross-reactive serotype 20B met the superiority criterion. In the immunobridging endpoint, VAX-31 met non-inferiority across all 32 serotype comparisons in adults aged 18-49 versus 50-64, with a safety profile similar to PCV20 and PCV21.

Why it matters: VAX-31 is designed to bring the serotype coverage of PCV20 and PCV21 into a single vaccine, with the potential to cover an additional 13-36% of invasive pneumococcal disease and 19-31% of pneumococcal pneumonia compared with currently available adult vaccines. The company said the OPUS-1 results will form the cornerstone of a planned Biologics License Application (BLA) to the US Food and Drug Administration.

Read more: Vaxcyte, 5 October 2026