Global pharma giant Pfizer has unveiled encouraging Phase 2 results for its investigational 25-valent pneumococcal conjugate vaccine candidate in infants.

 

In fact, the vaccine candidate PF-07872412 (25vPnC) has, in infants, shown stronger immune responses than the currently used PREVNAR 20 across all evaluated serotypes.

 

The randomized Phase 2 study compared a four-dose infant schedule of 25vPnC with PREVNAR 20 at 2, 4, 6, and 12–15 months, assessing safety, tolerability, and immune response.

 

The standout finding was a sharp immune boost against serotype 3, a persistent disease driver in children. One month after Dose 3, geometric mean titers were 8.8-fold higher with 25vPnC than with PREVNAR 20. After Dose 4, the difference widened further to approximately 15-fold higher.

 

Pfizer says the broader dataset across all 25 serotypes strengthens confidence that the program can meet non-inferiority thresholds in its upcoming Phase 3 pediatric trials.

 

The company also highlighted the vaccine’s projected reach, stating it could cover up to 90% of disease-causing serotypes in children under five, including roughly 15% attributable to serotype 3.

 

“For more than 25 years, our vaccines have helped protect children from pneumococcal disease, yet significant disease burden remains,” said Annaliesa Anderson, Senior Vice President and Chief Vaccines Officer, Pfizer. 

 

“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. We are advancing our Phase 3 program with the goal of delivering broader and more durable protection for children.”

 

The safety profile of 25vPnC was reported to be consistent with existing pneumococcal vaccines, with the most common reactions including injection-site redness, swelling, and pain.

 

Building on these findings, Pfizer has already launched a pivotal pediatric Phase 3 program in May 2026, enrolling up to 2,400 infants. The study will directly compare 25vPnC against the licensed 20-valent vaccine, with all participants receiving the same assigned vaccine across the full four-dose schedule.

 

If successful, 25vPnC would expand coverage to 25 serotypes—five more than current standard vaccines—potentially protecting against about 90% of pneumococcal disease-causing strains in U.S. children.

 

In parallel, Pfizer is also shifting its long-term adult strategy toward an even broader fifth-generation 35-valent vaccine candidate. That program, expected to enter clinical development by the end of 2026 pending regulatory alignment, aims to extend serotype coverage further while improving immune responses to key strains, including serotype 3, using next-generation technology.