Vaxcyte’s 31-valent vaccine hits primary endpoints, sending shares up 57%

Key points

• VAX-31 met all primary immunogenicity endpoints in the Opus-1 trial, which compared it against Pfizer’s Prevnar 20 and Merck’s Capvaxive in adults aged 50 and older.
• The vaccine demonstrated non-inferiority for all 20 strains targeted by Prevnar 20 and 17 of the 19 serotypes targeted by Capvaxive, using a stringent lower bound of the 95% confidence interval threshold of 0.667.
• Vaxcyte’s proprietary carrier-sparing technology allowed the vaccine to cover 31 serotypes without the typical reduction in antibody responses associated with adding more antigens to a single shot.
• The company expects to submit for FDA approval in the first half of 2028, with additional phase 3 trials (Opus-2 and Opus-3) and infant phase 2 data expected in the first half of 2027.
• VAX-31 is projected to provide incremental coverage of 13-36% of invasive pneumococcal disease and 19-31% of pneumococcal pneumonia compared to currently available adult vaccines.

Background

Vaxcyte’s success comes in a market dominated by Pfizer’s Prevnar franchise, which generated over $6 billion in revenue last year. While Merck and GSK have invested in competitors, Pfizer has maintained a strong market position. Vaxcyte’s earlier 2024 data had surprised analysts by showing non-inferiority despite the added complexity of covering more strains, a feat enabled by its unique conjugation technology.

How outlets are covering it

Fierce Biotech emphasized the technical details of the non-inferiority metrics and the specific serotypes where VAX-31 missed the stricter threshold against Capvaxive (serotypes 3 and 12F), noting it still passed a historical lower threshold. BioPharma Dive highlighted the market impact, describing the results as a 'near best-case scenario' that surpassed Wall Street expectations, with analysts noting the data was 'very clean.' STAT focused on the competitive landscape, noting the trial involved over 3,500 adults and positioning VAX-31 as a direct challenger to the lucrative $8 billion annual pneumococcal vaccine market. All sources agreed on the safety profile, noting the vaccine was well-tolerated with mild-to-moderate adverse events that typically resolved within two days.

Why it matters

Vaxcyte’s success could disrupt the dominant market position of Pfizer and Merck in the pneumococcal vaccine space. By offering broader coverage of 31 serotypes, VAX-31 addresses gaps in protection for underrepresented populations and currently circulating disease-causing strains. The positive results validate the company’s proprietary technology and position it as a significant player in a growing market, potentially leading to a regulatory submission that could reshape the competitive landscape for adult pneumococcal vaccines.

What to watch

Vaxcyte will report results from two additional phase 3 trials, Opus-2 and Opus-3, in the first half of 2027. The company also plans to unveil data from a phase 2 study of VAX-31 in infants around the same time. The FDA approval application is expected in the first half of 2028, with the comparison against Capvaxive likely to be a key focus for regulators due to the broader coverage of disease-causing serotypes.