Pfizer has reported findings from a Phase II trial assessing PF-07872412 (25vPnC), its investigational 25-valent pneumococcal conjugate vaccine candidate, in infants.
The results showed that a four-dose regimen provoked immune responses against all 25 assessed serotypes.
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Safety and tolerability profiles were comparable to four doses of Pneumococcal 20-valent Conjugate Vaccine (PREVNAR 20).
According to findings, immune responses occurred across every evaluated serotype one month following the third and fourth doses.
These included five additional serotypes, 15A, 23A, 23B, 24F, and 35B, estimated to cause a further 30% of paediatric invasive pneumococcal disease cases in the US compared with PREVNAR 20.
The candidate specifically targets serotype 3, responsible for 10.6% of invasive cases in US children aged under five years.
Compared with PREVNAR 20, geometric mean concentrations for serotype 3 were 8.8 times higher one month after the third dose and 15 times higher one month after the fourth dose.
Assays measuring opsonophagocytic activity also showed booster effects across all 25 serotypes one month after the fourth dose.
Adverse events, systemic occurrences, and local reactions remained balanced between the 25vPnC and PREVNAR 20 cohorts, reflecting medical conditions typical for healthy infants. Investigators recorded no related serious adverse events.
Pfizer senior vice-president and chief vaccines officer Annaliesa Anderson said: “These encouraging data build on more than 25 years of progress in protecting children from serious pneumococcal disease with PREVNAR vaccines.
“By expanding serotype coverage and applying next-generation technology to the historically challenging serotype 3, this candidate aims to extend the substantial reductions in disease that existing vaccines have achieved.
“If successful, it could help provide children with the broadest protection against invasive pneumococcal disease to date.”
The findings support Pfizer’s paediatric Phase III programme. Launched earlier in 2026, the programme includes three trials evaluating up to 6,830 children randomised to receive either 25vPnC or PREVNAR 20.
The serotypes in 25vPnC represent around 84% of invasive pneumococcal disease cases among US children younger than five years old.
Pfizer has also completed participant enrolment in an additional Phase III trial assessing manufacturing consistency across three separate lots of 25vPnC.
Separately, the company aims to advance an adult fifth-generation, 35-valent vaccine candidate into clinical studies before the close of 2026, subject to regulatory alignment.
In June, Pfizer reported topline data from the Phase III SigVie-002 study investigating sigvotatug vedotin in adults with previously treated, locally advanced or metastatic non-squamous non-small cell lung cancer (NSCLC).
