Pfizer (NYSE: PFE) reported Phase II results for its 25-valent pneumococcal conjugate vaccine candidate PF-07872412 (25vPnC) in healthy infants. The immunogenicity data showed substantially higher serotype 3 responses compared with Prevnar 20 (pneumococcal 20-valent conjugate vaccine), supporting the company's decision to initiate a pivotal Phase III pediatric program. The readout, presented at the International Society of Pneumonia and Pneumococcal Diseases meeting in Copenhagen, positions the Pfizer pneumococcal vaccine candidate as a potential successor to the current 20-valent standard of care.
In the Phase II study NCT06524414, infants received a four-dose series of either 25vPnC or Prevnar 20 at months 2, 4, 6, and 12–15. Geometric mean titers for serotype 3 were 8.8-fold higher with 25vPnC than with Prevnar 20 one month after dose 3 (4.22 vs. 0.48), rising to approximately 15-fold higher one month after dose 4 (13.85 vs. 0.92), the company said. The safety and tolerability profile of 25vPnC was consistent with currently approved pneumococcal vaccines, with the most common local reactions being redness, swelling, and injection-site pain. No safety concerns were identified.
The Phase II study is a randomized trial in healthy infants that enrolled participants beginning in July 2024, evaluating immunogenicity one month after dose 3 and one month after dose 4 across all 25 serotypes. The data presented reflect preliminary results from the broader study; full immunogenicity results across all serotypes were not disclosed in the press release, and the study remains ongoing. The company stated that immune responses observed for all 25vPnC serotypes from Phase II were strong compared with Prevnar 20, and that it is confident the required non-inferiority thresholds may be achieved in the Phase III program. The data remain preliminary and are based on interim findings from a study not yet fully reported.