Vaxcyte’s VAX-31 Challenges Pfizer and Merck in Pneumococcal Vaccine Market

Vaxcyte’s VAX-31 pneumococcal vaccine has shown promising results in a Phase 3 trial, potentially challenging Pfizer’s Prevnar 20 and Merck’s Capvaxive. The trial, involving 4,047 participants, found that VAX-31 matched Prevnar on all 20 shared serotypes and outperformed Capvaxive on 17 of 19. VAX-31 also covered three additional serotypes, which it exceeded in immune response compared to its rivals.

Pfizer stands to lose the most from this competition. The Prevnar franchise generated $6.49 billion in 2025, accounting for about 10% of Pfizer’s total revenue. However, Prevnar’s sales grew only 1% last year, and Pfizer cited lower US market share as a key issue. Meanwhile, Merck’s Capvaxive brought in $759 million in 2025, a smaller but growing segment of its business.

The financial impact on the companies differs significantly. Pfizer trades at 9.87x next twelve months (NTM) earnings, while Merck is at 16.36x. VAX-31 is not expected to file for approval until the first half of 2028, leaving time for further developments. Vaxcyte plans to release additional trial results in the first half of 2027, which could influence the competitive landscape.

VAX-31’s success could reshape the pneumococcal vaccine market, particularly for adults aged 50 and older. Vaxcyte estimates that VAX-31 covers serotypes responsible for about 95% of invasive pneumococcal disease in this age group. The upcoming results from OPUS-2 and OPUS-3 trials will be crucial in determining VAX-31’s future approval and market potential.