Pfizer advances pivotal pediatric pneumococcal vaccine development to address the growing need for broader protection against invasive pneumococcal disease (IPD) in infants. On May 20, 2026, Pfizer Inc. (NYSE: PFE) announced the commencement of its Phase 3 clinical trial for PF-07872412, a 25-valent pneumococcal conjugate vaccine (25vPnC) candidate. This decision follows robust Phase 2 results demonstrating that the investigational vaccine elicited significantly higher immune responses compared to the current standard-of-care, Prevnar 20.
The Phase 2 study evaluated the safety and immunogenicity of a four-dose series in healthy infants. Notably, the 25vPnC candidate showed a nearly 15-fold higher immune response against serotype 3, a persistent and dangerous driver of pediatric pneumonia and invasive disease, compared to Prevnar 20 after the fourth dose. By adding five new serotypes (15A, 23A, 23B, 24F, and 35B), this next-generation vaccine aims to cover approximately 90% of the bacterial strains currently causing disease in children under five.
Breaking Down the Pediatric Phase 3 Program
The pivotal Phase 3 program, which officially began in May 2026, is a randomized, double-blind study designed to evaluate the safety, tolerability, and immunogenicity of the 25vPnC candidate in approximately 2,400 healthy children. Participants are randomized to receive either the experimental 25-valent vaccine or the licensed 20-valent vaccine at 2, 4, 6, and 12–15 months of age.
These Phase 2 results reinforce our confidence in a next-generation vaccine designed to expand protection across serotypes while improving responses to key residual disease drivers such as serotype 3.
Learn MoreAnnaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer
Strategic Shift in Adult Vaccine Candidates
In a parallel strategic move, Pfizer announced it will bypass a 25-valent version for adults and move directly to a fifth-generation 35-valent vaccine candidate. This candidate leverages proprietary technology to maximize coverage and enhance the immune response to critical serotypes. Pfizer expects this 35-valent adult candidate to enter clinical development by the end of 2026, ensuring the company remains competitive against emerging rivals in the adult immunization market.
Available Clinical Data
| Vaccine Candidate | Serotype Count | Target Population | Status (as of May 2026) |
| 25vPnC (PF-07872412) | 25 | Pediatric (Infants) | Phase 3 (Pivotal) |
| Prevnar 20 (PCV20) | 20 | Pediatric & Adult | Licensed Standard |
| 5th Gen Candidate | 35 | Adult | Clinical Entry late 2026 |
| Serotype 3 Response Metric | Prevnar 20 (Control) | 25vPnC (Investigational) | Fold Increase |
| Post-Dose 3 (GMTs) | Baseline | 8.8x higher | 8.8x |
| Post-Dose 4 (GMTs) | Baseline | ~15x higher | 15.0x |
