Pfizer advances pivotal paediatric pneumococcal vaccine programme following strong positive phase 2 results

Pfizer Inc. announced data from its phase 2 study (NCT06524414) evaluating the safety, tolerability and immunogenicity of a four-dose series of its investigational 25-valent pneumococcal conjugate vaccine candidate PF-07872412 (25vPnC) in infants compared to four doses of Prevnar 20 at months 2, 4, 6 and 12-15. Based on the strong immune responses observed for all 25vPnC serotypes from phase 2, compared to Prevnar 20, Pfizer is confident that the required non-inferiority thresholds may be achieved for the 25vPnG paediatric phase 3 programme.

Key preliminary data from the broader phase 2 study were presented in an oral presentation at the 14th meeting of the International Society of Pneumonia & Pneumococcal Diseases in Copenhagen, Denmark (ISPPD). Results found:

One month after Dose 3, geometric mean titers for serotype 3 were 8.8-fold higher with 25vPnC than with Prevnar 20 ( 4.22 vs. 0.48).
One month after Dose 4, geometric mean titers for serotype 3 were approximately 15-fold higher with 25vPnC than with Prevnar 20 (13.85 vs. 0.92).
This vaccine candidate is expected to cover up to 90% of disease-causing serotypes in children under 5 years of age, which includes approximately 15% from serotype 3.
“For more than 25 years, our vaccines have helped protect children from pneumococcal disease, yet significant disease burden remains,” said Annaliesa Anderson, Ph.D., 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 programme with the goal of delivering broader and more durable protection for children.”

The phase 2 study is a randomized trial in healthy infants, with initial enrolment beginning in July 2024, evaluating 25vPnC compared with Prevnar 20. Participants were randomized to receive 25vPnC or Prevnar 20 at months 2, 4, 6 and 12–15 assessing the safety and tolerability, including local and systemic reactogenicity within seven days after each vaccination, as well as adverse events and serious adverse events in participants who receive at least one dose. The trial also assessed immunogenicity one month after Dose 3 and one month after Dose 4, compared to one month after Dose 3 and Dose 4 with Prevnar 20.

The safety and tolerability profile of 25vPnC was consistent with the currently approved and available pneumococcal vaccine. The most common local reactions were redness, swelling or pain at injection site similar to existing vaccines.

Despite significant reduction in pneumococcal disease burden by the currently available 20-valent standard-of-care-vaccine, serotype 3 remains a notable cause of invasive pneumococcal disease and complicated pneumonia in children. Therefore, based on this phase 2 data and discussions with regulatory authorities, Pfizer began a pivotal paediatric phase 3 programme in May 2026. The studies evaluate safety, tolerability and immunogenicity of 25vPnC in healthy children where participants receive either 25vPnC or PCV20 at 2, 4, 6 and 12 to 15 months of age. Participants will receive the same vaccine for all four vaccinations for up to 2,400 individuals comparing 25vPnC to the currently licensed 20-valent standard-of-care vaccine.

The vaccine candidate covers 25 serotypes including serotype 3, adding five new serotypes to the established vaccine coverage for infants. If successful, this has the potential to broaden protection to about 90% of disease-causing serotypes in US children.

Meanwhile, as the strongest opportunity to maintain the company’s current leadership in the adult market over the long term, Pfizer has decided to move directly to a fifth-generation vaccine candidate covering 35 serotypes. This fifth-generation adult candidate has the potential to increase serotype coverage while also improving immunogenicity for critical serotypes including serotype 3 with Pfizer’s proprietary next generation technology. The adult vaccine candidate is expected to enter clinical development by the end of 2026, pending alignment with regulatory authorities.

Pfizer's 4th-generation pneumococcal conjugate vaccine candidate builds on the 20 serotypes already covered by PCV20 (Prevnar 20). It adds five additional serotypes — 15A, 23A, 23B, 24F, and 35B that represents additional 25% coverage of IPD cases compared with PCV20 to broaden coverage to 25 serotypes total, including cross-reactivity. Beyond expanding serotype coverage, 25vPnC also aims to enhance protection against serotype 3, which remains a key driver of residual pneumococcal disease. To achieve this, 25vPnC utilizes next-generation technology specifically designed to elicit a more robust immune response against serotype 3.

Prevnar 20 is a vaccine approved for:
the prevention of invasive disease caused by 20 Streptococcus pneumoniae strains (1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F) in individuals 6 weeks of age and older.
the prevention of otitis media (middle ear infection) caused by 7 of the 20 strains in individuals 6 weeks through 5 years.
active immunization for the prevention of pneumonia caused by Streptococcus pneumoniae strains 1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F in individuals 18 years of age and older.
The indication for the prevention of pneumonia caused by S. pneumoniae serotypes 8, 10A, 11A, 12F, 15B, 22F, and 33F in individuals 18 years of age and older is approved based on immune responses. Continued approval may depend on a supportive study.

Pfizer apply science and our global resources to bring therapies to people that extend and significantly improve their lives. The company strive to set the standard for quality, safety and value in the discovery, development, and manufacture of health care products, including innovative medicines and vaccines.

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