Pfizer details 25‑strain infant vaccine data as pivotal trials advance
A 401-infant presentation compared immune responses and safety with Prevnar 20; the company has not dated its pediatric Phase 3 readout.
Adrian Kessler
Antibody responses against 25 pneumococcal strains supported a broader infant vaccine as Pfizer Inc. NYSEPFE presented detailed Phase 2 results on Oct. 24. The experimental shot adds five strains to Prevnar 20, but the study measured immune responses and safety rather than a reduction in infections.
The presentation covered 401 healthy full-term infants receiving the candidate, PF-07872412, or Prevnar 20 in a randomized study. Safety was the primary objective, and Pfizer reported no related serious adverse events. Larger pivotal trials are already under way.
Pfizer is a large United States drugmaker with a global medicines and vaccines business.
Pfizer shares NYSEPFE closed at US$30.03 on the NYSE at 4:02 p.m. EDT on Oct. 23, according to Google Finance. That close preceded the Saturday presentation and provides no measure of the market's response to it.
Safety Was The Primary Objective
The Oct. 24 presentation describes a four-dose series, with immune responses assessed a month after the third and fourth doses as a secondary objective. After the first dose, fever was reported in 24.8 per cent of candidate recipients and 23.1 per cent of comparator recipients.
Pfizer described local reactions and systemic events as mostly mild to moderate, with adverse events balanced between groups. Injection-site pain after the first dose occurred in 63.4 per cent of candidate recipients and 53.8 per cent of comparator recipients.
The candidate generated antibody concentrations against serotype 3 about 15 times those of Prevnar 20 a month after the fourth dose. The corresponding comparison after the third dose was 8.8 times. Pfizer also reported functional antibody responses against every targeted strain after the final dose.
Those serotype 3 comparisons had already appeared in Pfizer's May 20 announcement; the October presentation supplies further detail rather than a new topline result. The Oct. 24 release gives no confidence intervals or formal non-inferiority margins for its immune-response comparisons.
Pfizer said discussions with regulatory authorities preceded the pivotal program's start in May. The releases provide no FDA comments specifying an agreed statistical threshold, so the company's confidence in the design cannot be treated as an agency finding.
"If successful, it could help provide children with the broadest protection against invasive pneumococcal disease to date," Pfizer chief vaccines officer Annaliesa Anderson said in the Oct. 24 release.
Pivotal Trials Face An Established Competitor
Merck & Co., Inc. NYSEMRK already markets Vaxneuvance, whose United States prescribing information revised in June 2026 covers prevention of invasive disease from 15 pneumococcal strains. It is indicated from six weeks of age and uses a four-dose infant series.
Merck shares NYSEMRK closed at US$145.27 at 4:01 p.m. EDT on Oct. 23 on the NYSE, according to Google Finance. Pfizer is testing its candidate against its own licensed vaccine, rather than reporting a direct comparison with Merck's product.
Pfizer's October presentation estimates potential coverage of roughly 84 per cent of invasive pneumococcal infections in United States children younger than five. That estimate includes cross-protection and uses surveillance averaged over 2020 through 2024; it is not a measured reduction in disease in this trial.
Pfizer's Aug. 4 financial report recorded US$5.3 billion of internal research and development investment during the first half of 2026. The Oct. 24 vaccine announcement disclosed no dedicated development budget or cash runway.
The infant program includes three Phase 3 studies with up to 6,830 participants randomized to the candidate or Prevnar 20. Pfizer also said a manufacturing-lot consistency study had completed enrolment, but supplied no pediatric Phase 3 readout date.
The next scheduled investor checkpoint is Pfizer's Nov. 3 quarterly results call, which will cover its third-quarter financial performance. Its next dated vaccine milestone is the planned start of clinical development for a separate 35-strain adult candidate by the end of 2026, subject to regulatory alignment.
