Pfizer 25-Valent PCV Shows Breadth Versus Prevnar 20 But Pivotal Proof Still Missing

Pfizer's 25vPnC Shows Robust Phase 2 Data in Infants

Pfizer Inc. announced detailed Phase 2 study results for its investigational 25-valent pneumococcal conjugate vaccine candidate, PF-07872412 (25vPnC), in infants. The study (NCT06524414) demonstrated robust immune responses against all 25 serotypes and showed safety and tolerability comparable to PREVNAR 20®. These findings, presented at IDWeek 2026, support the ongoing Phase 3 development program for 25vPnC, which, if successful, could provide protection against serotypes responsible for approximately 84% of invasive pneumococcal disease (IPD) cases among children under five years of age in the U.S.

• The 25-valent vaccine candidate (25vPnC) elicited robust immune responses against all 25 serotypes, including five new serotypes (15A, 23A, 23B, 24F, and 35B), one month after both Dose 3 and Dose 4. Its safety and tolerability profile was comparable to PREVNAR 20® in healthy infants, with adverse events consistent with conditions commonly diagnosed in this age group and no related serious adverse events.
• 25vPnC demonstrated an enhanced immune response against serotype 3, a historically challenging serotype accounting for 10.6% of IPD in U.S. children under five. It generated geometric mean concentrations (GMCs) that were 8.8-fold higher one month after Dose 3 and approximately 15-fold higher one month after Dose 4 compared to PREVNAR 20®, utilizing next-generation technology.
• These positive Phase 2 results support the advancement of 25vPnC into three ongoing Phase 3 studies, enrolling up to 6,830 participants. If approved, 25vPnC aims to offer the broadest protection against invasive pneumococcal disease for pediatric populations in the U.S., covering serotypes estimated to cause approximately 84% of IPD cases in children under five.

Why Broader Protection Against Pediatric IPD is Needed

Pediatric invasive pneumococcal disease in the late PCV13 era remains clinically severe with marked serotype replacement, while adult burden concentrates in older adults and those with immunocompromising and chronic conditions. Higher-valency vaccines expand coverage to approximately half of circulating serotypes but leave residual gaps linked to emerging non-vaccine serotypes and low uptake. These patterns focus unmet need on broader protection, risk-based adult strategies, and equity in surveillance and access.

• Hospitalized children with serotype replacement disease: Among 136,018 hospital discharges in 6 pediatric sentinel hospitals in Argentina (October 2022-September 2025), 218 IPD cases were identified (16.0 per 10,000; 95% CI, 14.0-18.3), with highest rates in children aged 2-4 years (26.5 per 10,000; 95% CI: 20.6-33.5). Pneumonia predominated (65.6%), often complicated by pleural effusion/empyema or necrotizing disease, 18.9% required mechanical ventilation, meningitis occurred in 14.7%, and case fatality was 5.0%. Among 119 serotyped isolates, 30.3% were PCV13, 21.0% additional PCV20 and 48.7% non-PCV20 serotypes, yielding an estimated PCV20 coverage of 51.3%, with sepsis (adjusted odds ratio [aOR] 20.82; 95% CI: 4.23-102.58) and meningitis (aOR 10.75; 95% CI: 2.10-54.95) strongly associated with mortality.

• Children with sickle cell disease, HIV and other immunocompromising or chronic conditions: In children with immunocompromising conditions, VE against PCV13-type IPD ranged between 83.8% and 91%. In Metropolitan Atlanta, IPD declined by 87% in children with HbSS aged 0 to 4 years and by 80% in those aged 5 to 9 years from 1994-1999 to 2010-2018, yet incidence rate ratios versus the reference population increased from 20.2 to 29.2, and after 2010 all IPD serotypes were not included in PCV13. PPSV23 would cover 62% of non-PCV13 serotype IPD in children with SCD, whereas PCV15, PCV20, and PCV21/V116 could cover 16%, 51%, and 92%, respectively.

• Adults with high-risk immunocompromising conditions and multimorbidity: Highest IRRs (95% CIs) for adult IPD were reported in transplant recipients 30.75 (17.64-53.60), asplenia 24.29 (18.63-31.65), people living with human immunodeficiency virus (PLWH) 21.87 (15.72-30.43), and haematological malignancy 19.63 (11.10-34.71), with IRRs >10 also observed for compromised cerebrospinal fluid barrier and Down syndrome. In Catalonia in persons ≥50 years-old, maximum incidence rates emerged among persons with history of previous IPD or all-cause pneumonia, followed by haematological neoplasia (475.0), HIV-infection (423.7), renal disease (384.9) and chronic respiratory disease (314.7) per 100,000 person-years, with rates of 42.1, 89.9, 201.1, 350.9, 594.3 and 761.2 in persons with 0, 1, 2, 3, 4 and ≥5 comorbidities, respectively.

• Older adults with high severity, mortality and long-term sequelae: In northern Italy 2012-2024, most cases occurred in males aged ≥65, bacteremia with pneumonia was the most frequent presentation (55.6%), and vaccine-preventable serotypes accounted for 64% of cases, mostly (56%) in patients aged ≥65. In São Paulo in adults aged 60+ hospitalized with IPD, hospitalization lasted a median of ten days, with 53% requiring ICU admission, and case fatality rate was 43%. In England in individuals aged 65 years or older, increased all-cause mortality was observed in IPD cases versus comparators (hazard ratio 3.74 [95% CI 3.50-3.99]), with predicted median survival of 4.7 years (IQR 2.9-7.4) versus more than 11.9 years (IQR 8.7 to >11.9).

• Indigenous, LMIC and other populations affected by coverage gaps and replacement serotypes: PCV21's deliberate omission of serotypes 4, 6A, 9V, and 10A creates coverage gaps for Indigenous communities where serotype 4 has re-emerged. Multidrug-resistant lineages expressing serotypes 15A, 15C, and 35B are expanding in the post-PCV13 era, and in Granada the most frequent serotypes were 8, 3, 22F, 9N and 11A, with more than 30% of serotypes not included in pneumococcal vaccines currently used in Spain. The mismatch between surveillance infrastructure in high-income countries and LMIC settings, where the greatest burden is concentrated, represents a structural inequity limiting global applicability of current policies.

• Patients at risk for drug-resistant disease and meningitis with limited therapeutic options: Macrolide resistance was detected in 26.9% of isolates and beta-lactam resistance in 14.9% in northern Italy, and in Latin America and the Caribbean resistance to penicillin was 21.7% (95%IC 18.7-25.0) and for ceftriaxone/cefotaxime 4.7% (95%IC 3.2-6.9). Ceftriaxone minimum inhibitory concentration creep among phenotypically susceptible isolates presents risk particularly in meningitis where cerebrospinal fluid penetration is inherently limited. Of the four novel agents approved for community-acquired bacterial pneumonia — ceftaroline, lefamulin, omadacycline, and delafloxacin — none have established pharmacokinetic or clinical efficacy data supporting use in pneumococcal meningitis.

• Under-vaccinated at-risk and high-risk adults targeted for simplified uptake: No previous pneumococcal vaccination was shown in 106 (58.6%) patients with IPD in Granada, only 7.3% had received pneumococcal vaccination among 110 individuals with details in Western Sydney, and 90% had unknown vaccination status in São Paulo. In Belgium, 2,120 cases of IPD were reported in 2024 with uptake of 13-24% in risk groups, and 2025 guidelines replace sequential regimens with a single-dose conjugate approach: PCV20 for adults 18-49 years with risk conditions (serotype 4 coverage critical), PCV20 or PCV21 for ages 50-84 years, and PCV21 preferred for adults ≥85 years (15% coverage advantage).

Unpacking the Robust Phase 2 Data for 25vPnC

Key trials in invasive pneumococcal disease span reduced-dose schedule evaluations, population-based surveillance, and phase 2 and phase 3 conjugate vaccine studies. Designs include cluster-randomised infant schedules, active surveillance comparisons, and randomised immunogenicity trials in infants, adults, and high-risk groups. Endpoints centre on vaccine-type carriage prevalence, IPD incidence by serotype and syndrome, and opsonophagocytic activity, IgG, and safety.

• Viet Nam PCV10 cluster-randomised trial (NCT02961231): 24 communes in Nha Trang randomly assigned (1:1:1:1; six communes per group) to 0p+1 (single dose at age 12 months), 1p+1 (doses at ages 2 and 12 months), 2p+1 (doses at ages 2, 4, and 12 months), or 3p+0 (doses at ages 2, 3, and 4 months), with three unvaccinated communes as observational comparison; prespecified primary outcome was non-inferiority of 1p+1 versus standard-dose (2p+1, 3p+0) for prevalence of VT carriage in vaccine-eligible infants (aged 4-11 months) and toddlers (aged 14-24 months) in 2022 (5.5 years after vaccine introduction), with non-inferiority defined as upper bound of the 95% CI of the difference in VT carriage prevalence not exceeding 5 percentage points (pp); prespecified secondary objective evaluated the 0p+1 schedule and indirect effects in adult caregivers and preschool children (aged 3-4 years).

• US PCV7 surveillance 1998-2007: laboratory-confirmed IPD cases identified by 8 active population-based surveillance sites; compared overall, age group-specific, syndrome-specific, and serotype group-specific IPD incidence in 2007 with that in 1998-1999 (before PCV7) and assessed potential serotype coverage of new conjugate vaccine formulations.

• V114 PNEU-AGE phase 3 in adults ≥50 years of age: participants randomized 1:1 to single dose of V114 or PCV13, stratified by age (50-64 years, 65-74 years, and ≥75 years); serotype-specific opsonophagocytic activity (OPA) and immunoglobulin G (IgG) antibodies measured prior to and 30 days after vaccination (Day 30); primary objectives included assessing noninferiority of V114 to PCV13 for the 13 shared serotypes and superiority for the two unique serotypes (22F, 33F), with superiority for shared serotype 3 as secondary objective; adverse events collected following vaccination.

• V114-008 phase 2 in healthy infants 6-12 weeks old: randomized to 4-dose regimen of V114 Lot 1, V114 Lot 2 or PCV13 at 2, 4, 6 and 12-15 months old; primary immunogenicity endpoint was noninferiority of V114 Lot 1 and V114 Lot 2 relative to PCV13 based on proportion achieving serotype-specific IgG concentration ≥0.35 µg/mL for 13 shared serotypes at 1 month postdose 3 (PD3); serotype-specific IgG geometric mean concentrations measured at PD3, predose 4 and 1 month postdose 4 (PD4), with adverse events evaluated after each dose.

• STRIDE-13 phase 3 V116 in children 2 to <18 y with increased risk: individuals with diabetes mellitus, chronic heart, chronic lung, chronic kidney, and/or chronic liver disease who had previously completed a primary pneumococcal vaccination regimen randomized 3:2 to single dose of V116 (n=531) or PPSV23 (n=351); immunogenicity assessed at 30 d postvaccination comparing OPA geometric mean titers (GMTs) and IgG geometric mean concentrations (GMCs), with noninferiority for 12 shared serotypes and superiority for 9 unique serotypes based on OPA GMTs; safety evaluated by proportion with adverse events (AEs).

• STRIDE-7 phase 3 V116 in adults living with HIV: two-part trial at 20 centres in Belgium, Chile, France, South Africa, Thailand, and the USA; Part A randomised (1:1) adults aged 18 years or older (CD4 counts ≥50 cells per μL, plasma HIV RNA load <50 000 copies per mL, and combination antiretroviral therapy for ≥6 weeks) to V116 followed by placebo 8 weeks later or 15-valent PCV (PCV15) followed by 23-valent pneumococcal polysaccharide vaccine (PPSV23) 8 weeks later; primary outcome in per-protocol population was serotype-specific opsonophagocytic activity geometric mean titres 30 days post-vaccination for 13 common serotypes plus 8 unique to V116; Part B was open-label PCV15 after V116.

25vPnC's Potential in the Evolving IPD Vaccine Landscape

Adjunctive treatment with daptomycin and an anti-C5 antibody was superior to adjunctive dexamethasone in C57BL/6 mice infected by injection of pneumococci into the cisterna magna with treatment begun 21 h after infection and follow-up until 45 h after infection. Disease symptoms were reduced (clinical score 1.1 ± 1.1 versus 5.0 ± 2.7, p < 0.0083), explorative activity was improved (open field test 17.8 ± 8.2 versus 7.4 ± 4.3 crossed fields/2 minutes, p < 0.0083), and hearing impairment was reduced (thresholds for click stimulus 96.1 ± 14.7 versus 114.8 ± 9.3 dB SPL, p < 0.0083) in the acute stage. In long-term follow-up at 2 weeks after infection, explorative activity (14.4 ± 7.3 crossed fields/2 minutes versus 6.3 ± 7.2, p < 0.05) and cognitive function (t-maze test, exploration time previously unknown alley 72.4 ± 14.3 versus 48.7 ± 25.6%, p < 0.05) was improved. Treatment with daptomycin plus an anti-IL-1β antibody or roscovitine was not of significant benefit in comparison to adjunctive therapy with dexamethasone.

For prevention of invasive disease and pneumonia caused by S. pneumoniae in adults, the 20-valent pneumococcal conjugate vaccine (PCV20; Prevnar20; Apexxnar) contains all components of PCV13 with the addition of polysaccharide conjugates of seven more serotypes, selected based on their generalised geographic distribution and relative prevalence as a cause of pneumococcal disease. PCV20 administered as a single dose by intramuscular injection induced robust immune responses to all 20 S. pneumoniae serotypes covered by the vaccine and was well tolerated, with a tolerability and safety profile similar to that for PCV13. A nonadjuvanted whole-inactivated vaccine (Gamma-PN) induced comparable or superior opsonophagocytic killing assay (OPKA) responses in rabbits to the licensed Prevnar 13 vaccine (PCV13) for vaccine-included serotypes, and a superior response to nonincluded serotypes, including emergent 22F and 35B, with administration of Gamma-PN without adjuvant resulting in higher OPKA responses and improved protection compared to adjuvanted Gamma-PN.

Pfizer's 25-Valent PCV: Raising the Bar in Pediatric Protection

The recent announcement of positive Phase 2 data for Pfizer's 25-valent pneumococcal conjugate vaccine (25vPnC) in infants signals a pivotal moment in the evolution of pneumococcal disease prevention. With robust immune responses across all 25 serotypes and a safety profile comparable to PREVNAR 20®, this investigational vaccine is positioned to significantly expand protection against Streptococcus pneumoniae.

For decades, pneumococcal conjugate vaccines (PCVs) have dramatically reduced the burden of invasive pneumococcal disease (IPD) and other infections. However, the success of these vaccines has been consistently met with the challenge of serotype replacement, where non-vaccine serotypes emerge and cause disease. Studies indicate that even after the introduction of 13-valent PCVs, non-PCV13 serotypes have increased, contributing to a substantial number of pediatric outpatient visits for acute respiratory infections and associated antibiotic use. A 25-valent vaccine, by targeting a broader spectrum of serotypes responsible for a significant proportion of IPD in young children, directly addresses this evolving epidemiological landscape.

This development carries substantial strategic implications. For Pfizer, it represents an opportunity to solidify its leadership in the pediatric vaccine market, potentially setting a new benchmark for comprehensive protection. The introduction of such a high-valency vaccine would likely accelerate the shift in global immunization strategies, pushing for the adoption of broader-spectrum PCVs to counter the persistent threat of emerging serotypes. This, in turn, places considerable pressure on competitors, who are also advancing their own higher-valent candidates, to match or exceed this level of coverage.

However, the path forward is not without its considerations. The inherent dynamism of pneumococcal serotypes means that even with 25 valencies, the risk of further serotype replacement, albeit reduced, cannot be entirely eliminated. Furthermore, the complexity of formulating and ensuring consistent, robust immunogenicity across such a large number of serotypes is a scientific and manufacturing challenge. While the Phase 2 data are promising, continued vigilance in Phase 3 and post-marketing surveillance will be crucial to confirm broad and sustained protection. The rapid pace of innovation in this space, with 21-valent, 24-valent, and 31-valent vaccines also in various stages of development, underscores a highly competitive environment where continuous innovation will be key to maintaining market relevance and public health impact.