Broader pneumococcal vaccine meets phase 3 immune-response goals

Available adult pneumococcal vaccines cover different serotypes, or bacterial types, creating tradeoffs in coverage. VAX-31 is designed to combine all types targeted by Prevnar 20 and Capvaxive, plus three additional types.

The investigational 31-valent vaccine met all prespecified primary endpoints in the phase 3 OPUS-1 trial, according to topline results announced by Vaxcyte. Based on circulating serotypes, the company estimates that VAX-31 targets types responsible for approximately 95% of invasive pneumococcal disease in US adults aged 50 years or older. This is a coverage estimate, not demonstrated vaccine effectiveness.

The randomized, double-blind trial enrolled 4,047 adults without prior pneumococcal vaccination. Adults aged 50 years or older received VAX-31, Prevnar 20, or Capvaxive. A smaller, younger cohort received VAX-31 or Prevnar 20. Immune responses were measured one month later.

In the primary analysis, VAX-31 met noninferiority criteria for all 28 serotypes shared with either comparator and superiority criteria for its three unique types and cross-reactive serotype 20B. Responses in younger adults also met noninferiority criteria compared with those aged 50–64.

Direct comparisons showed an important distinction: VAX-31 met the trial’s stricter standard for comparable immune responses for all 20 types shared with Prevnar 20, but only 17 of 19 shared with Capvaxive. Responses to the remaining two types, serotypes 3 and 12F, passed a less stringent standard used in earlier vaccine trials.

Safety was similar across vaccines. Reactions were generally mild to moderate, most resolved within 48 hours, and no serious adverse events were considered vaccine-related.

Vaxcyte expects additional phase 3 results in early 2027 and plans an FDA application in the first half of 2028.

“Important gaps remain in adult pneumococcal disease coverage, and OPUS-1 highlights VAX-31’s potential to address them,” said Luis Jodar, PhD, Vaxcyte’s chief medical officer.

Source: Vaxcyte. (2026 Oct 5) Vaxcyte reports positive topline data from OPUS-1, the pivotal adult phase 3 trial of VAX-31, the company’s 31-valent pneumococcal conjugate vaccine candidate