Pfizer unveils strong data for 25-valent vaccine

Unbranded pediatric vaccine vial and syringe in lab, illustrating strong data for 25-valent vaccine PFE

Key Points

01Pfizer (PFE) reports Phase 2 results for 25-valent pediatric pneumococcal vaccine PF-07872412
02Four-dose regimen generated immune responses to all 25 serotypes in infants
03Serotype 3 responses reached up to about 15-fold higher than Prevnar 20
04Three Phase 3 studies of the 25-valent candidate are underway in 2026

Pfizer highlights robust Phase 2 data at IDWeek 2026

Pfizer (PFE) has reported Phase 2 results for its investigational 25-valent pediatric pneumococcal conjugate vaccine candidate, PF-07872412, in healthy infants, with detailed findings presented at IDWeek 2026 in Washington, D.C. The vaccine was evaluated as a four-dose series and compared with Prevnar 20, Pfizer’s licensed 20-valent pneumococcal conjugate vaccine. Pfizer said the 25-valent candidate elicited immune responses against all 25 serotypes one month after the third dose and one month after the fourth dose.

A four-dose regimen of PF-07872412 elicited robust immune responses across all targeted serotypes.

Expanded serotype coverage and serotype 3 findings

The 25-valent candidate adds five serotypes beyond those included in Prevnar 20: 15A, 23A, 23B, 24F, and 35B. Pfizer stated that these five additional serotypes account for an additional 30% of pediatric invasive pneumococcal disease cases in the United States compared with Prevnar 20, citing surveillance data from 2020 to 2024. This expanded coverage is being investigated as part of efforts to address a broader range of circulating pneumococcal serotypes in children.

The study showed particularly notable responses against serotype 3. One month after the third dose, immune responses to serotype 3 were 8.8-fold higher with the 25-valent candidate than with Prevnar 20. One month after the fourth dose, serotype 3 responses were approximately 15-fold higher compared with Prevnar 20. Antibody concentrations for serotype 3 exceeded levels seen with Prevnar 20.

Progress into Phase 3 and pipeline plans

The pediatric 25-valent pneumococcal conjugate vaccine candidate has already advanced into Phase 3 development. Pfizer is conducting three Phase 3 studies that began in 2026, in which up to 6,830 participants are randomized to receive either the 25-valent candidate or Prevnar 20. Enrollment has been completed for a Phase 3 study intended to demonstrate manufacturing lot consistency for PF-07872412.

Beyond the pediatric program, Pfizer has outlined broader pneumococcal vaccine development plans. The company stated it intends to advance a 35-valent pneumococcal vaccine candidate for adults into clinical development by the end of 2026, pending regulatory alignment. This adult candidate is positioned alongside the pediatric 25-valent program as part of an expanded pneumococcal portfolio targeting more serotypes across age groups.

Key Takeaways

01Phase 2 data indicate that PF-07872412 can broaden pediatric pneumococcal serotype coverage while maintaining a safety profile comparable to Prevnar 20.
02Markedly higher serotype 3 responses suggest the candidate may address a historically challenging serotype within a single conjugate vaccine series.
03Ongoing Phase 3 trials and completed lot-consistency enrollment show the pediatric 25-valent program is progressing toward later-stage evaluation.
04The inclusion of five additional serotypes linked to a significant share of U.S. pediatric invasive disease underscores the strategic focus on epidemiologically relevant strains.
05Plans for a 35-valent adult candidate signal an effort to expand Pfizer (PFE)’s pneumococcal franchise across both pediatric and adult populations.

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