Vaxcyte said its Phase 3 pneumococcal conjugate vaccine VAX-31 met key co-primary immunogenicity endpoints in adults, sending the company’s shares sharply higher. The result sets up a potential expansion of serotype coverage and further intensifies competition in the large, established pneumococcal vaccine market. Across a randomized Phase 3 study enrolling just over 3,500 adults age 50 and older, VAX-31 was compared with Pfizer’s Prevnar and Merck’s Capvaxive on antibody responses across multiple bacterial strains. Vaxcyte emphasized its 31-valent design as a differentiator for broader protection. For biotech investors and clinical planners, the readout is a near-term signal that next-generation pneumococcal coverage could continue to progress through regulatory pathways, with commercial implications for payers and healthcare systems managing vaccine portfolios by serotype breadth.