Vaxcyte, Inc. (PCVX) reported that the Phase 1/2 adult study of its 31‑valent pneumococcal conjugate vaccine (VAX‑31) was published in The Lancet Infectious Diseases on March 18, 2026. The study enrolled healthy adults aged 50 years and older and demonstrated that VAX‑31 was well tolerated and induced robust opsonophagocytic activity (OPA) and immunoglobulin G (IgG) responses across all 31 serotypes.
The data showed that VAX‑31 met or exceeded non‑inferiority criteria for the 20 serotypes shared with the current standard‑of‑care vaccine Prevnar 20, and achieved superiority for the 11 additional serotypes unique to VAX‑31. These results validate the company’s carrier‑sparing, site‑specific conjugation platform and confirm that the high‑dose formulation can deliver broader coverage without compromising immunogenicity.
The publication of these Phase 1/2 results underpins Vaxcyte’s plan to advance the high‑dose VAX‑31 into its Phase 3 OPUS program. The company expects topline data from the pivotal trial in the fourth quarter of 2026, a critical step toward regulatory approval and commercialization of a vaccine that could capture a larger share of the pneumococcal conjugate market.
The global pneumococcal conjugate vaccine market is estimated to exceed $8 billion and is projected to grow to more than $11 billion by 2035. VAX‑31’s 31‑valent coverage positions it to compete directly with Prevnar 20 and Merck’s Capvaxive, potentially becoming a “category killer” if the Phase 3 data confirm the Phase 1/2 findings. The broader serotype coverage could translate into higher market penetration, especially in adult populations where serotypes not covered by existing vaccines are increasingly prevalent.
The company’s management highlighted the significance of the data, noting that the results “further affirm the potential of our site‑specific, carrier‑sparing platform to deliver the broadest‑spectrum PCVs.” With the Phase 3 program underway, Vaxcyte is poised to advance a product that could reshape the pneumococcal vaccine landscape for adults and infants alike.
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