SAN CARLOS, Calif. — October 5, 2026

Vaxcyte, Inc. reported positive topline results from the pivotal OPUS-1 Phase 3 trial evaluating VAX-31, the company’s 31-valent pneumococcal conjugate vaccine (PCV) candidate for prevention of invasive pneumococcal disease (IPD) and pneumococcal pneumonia. VAX-31 met all prespecified primary immunogenicity and safety endpoints across the age groups studied compared with Prevnar 20 (PCV20) and/or Capvaxive (PCV21). In adults aged 50 and older, all 28 VAX-31 serotypes shared with PCV20 and/or PCV21 met the prespecified noninferiority criterion, while three VAX-31-specific serotypes and cross-reactive serotype 20B met the superiority criterion. Vaxcyte said the OPUS-1 results will serve as a cornerstone for its planned Biologics License Application (BLA), with the company expecting additional adult Phase 3 results from OPUS-2 and OPUS-3 in the first half of 2027.

VAX-31 Demonstrates Broad Immunogenicity

VAX-31 demonstrated broad immune responses across the serotypes evaluated in OPUS-1, supporting the potential of the candidate to expand pneumococcal coverage without compromising the magnitude of immune responses. Among adults aged 50 and older, all 28 shared serotypes met the prespecified OPA geometric mean ratio noninferiority threshold of a lower bound of the 95% confidence interval above 0.667. The three serotypes unique to VAX-31 and cross-reactive serotype 20B also met the prespecified superiority criterion. In individual comparator analyses, VAX-31 met the noninferiority criterion for 20 of 20 serotypes shared with PCV20 and 17 of 19 serotypes shared with PCV21. Serotypes 3 and 12F did not meet the more stringent >0.667 threshold against PCV21 but met the historical >0.5 threshold. The company said the results support the potential for VAX-31 to address gaps created by differences in serotype coverage among currently available adult pneumococcal vaccines.

OPUS-1 Confirms Safety Across Adult Groups

VAX-31 was well tolerated and showed a safety profile similar to PCV20 and PCV21 across all ages studied. OPUS-1 enrolled 4,047 participants at approximately 30 U.S. sites, including 3,572 adults aged 50 and older and 475 adults aged 18 to 49. Participants aged 50 and older were randomized to receive a single dose of VAX-31, PCV20 or PCV21, while the younger adult cohort received VAX-31 or PCV20. Frequently reported local and systemic reactions were generally mild to moderate, with most resolving within 48 hours. Vaxcyte reported that no serious adverse events were considered related to the study vaccines and no participants discontinued treatment because of adverse events. The prespecified immunobridging analysis also showed that VAX-31 met the noninferiority criterion across all 321 serotype comparisons between adults aged 18 to 49 and those aged 50 to 64.

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Vaxcyte Targets 2028 VAX-31 BLA Filing

The OPUS-1 results provide a clinical foundation for Vaxcyte’s planned regulatory strategy for VAX-31, while additional Phase 3 studies remain important to the development program. The company expects to report safety, tolerability and immunogenicity results from OPUS-2 and OPUS-3 in the first half of 2027, followed by a manufacturing consistency study and a planned BLA submission in the first half of 2028. VAX-31 is designed to provide broader protection against pneumococcal disease by covering 31 serotypes and maintaining coverage of historically important strains alongside currently circulating disease-causing serotypes. Vaxcyte estimates that the candidate could cover approximately 95% of IPD and 88% of pneumococcal pneumonia circulating among U.S. adults aged 50 and older. The company is also evaluating VAX-31 in infants in a Phase 2 program, while continuing development of additional vaccine candidates through its carrier-sparing and site-specific conjugation platform.

Source: Vaxcyte, press release