Merck Presents Systematic Review of Pneumococcal Serotypes Covered by CAPVAXIVE® in U.S. Adults
Merck & Co., Inc., known as MSD outside the United States and Canada, announced findings from a systematic literature review on the epidemiology and antimicrobial resistance (AMR) of pneumococcal serotypes targeted by CAPVAXIVE® (Pneumococcal 21-valent Conjugate Vaccine) in U.S. adults. The analysis evaluated 15 studies published between 2015 and 2025, focusing on serotypes covered by CAPVAXIVE but not PCV20 (CAPVAXIVE-unique serotypes: 9N, 15A, 15C, 16F, 17F, 20A, 23A, 23B, 24F, 31, 35B) compared with serotypes included in PCV20 but not CAPVAXIVE (PCV20-unique serotypes: 1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F). Results were presented at IDWeek 2025 in Atlanta, Georgia.
The review included 15 full-text U.S. publications alongside CDC Active Bacterial Core (ABC) Surveillance reports. Of these, 13 reported prevalence, five reported incidence, two reported mortality, two addressed AMR, one examined health resource utilization (HRU), and one evaluated complications of pneumococcal disease (PD). Overall, the findings indicate that CAPVAXIVE-unique serotypes are more prevalent in U.S. adults with PD than PCV20-unique serotypes. Additionally, PD caused by CAPVAXIVE-unique serotypes shows higher resistance to commonly prescribed antibiotics for non-invasive PD.
Key findings include:
- Prevalence in Older Adults: CDC ABC data from 2023 showed that among adults ≥65 years, invasive PD caused by CAPVAXIVE-unique serotypes accounted for 34.8% of cases—more than triple that of PCV20-unique serotypes (8.5%). In adults aged 50–64, CAPVAXIVE-unique serotypes accounted for ~30% of cases, compared to ~15% for PCV20-unique serotypes.
- Antimicrobial Resistance: Among hospitalized adults ≥18 years (2009–2017), AMR was reported for seven CAPVAXIVE-unique serotypes and one PCV20-unique serotype. Penicillin and erythromycin resistance was particularly high for serotypes 35B (96% and 89%, respectively) and 23A (72% and 46%). Multidrug resistance was highest for serotypes 19F (42%) and 23A (27%), with 19F covered by PCV20 and 35B and 23A covered by CAPVAXIVE.
CAPVAXIVE is approved in the U.S. for:
- Active immunization to prevent invasive disease and pneumonia caused by Streptococcus pneumoniae serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15B, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B in adults ≥18 years.
- Active immunization to prevent pneumonia caused by the same serotypes in adults ≥18 years.
CAPVAXIVE should not be administered to individuals with a history of severe allergic reactions, including anaphylaxis, to any vaccine component or diphtheria toxoid. The indication for pneumonia prevention is approved under accelerated approval based on immune response measured by opsonophagocytic activity (OPA), with continued approval dependent on confirmatory trials demonstrating clinical benefit.
“To help address the burden of pneumococcal disease, understanding the prevalence and antimicrobial resistance among pneumococcal serotypes is critical,” said Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines at Merck Research Laboratories. “CAPVAXIVE covers the serotypes responsible for the majority of invasive pneumococcal disease cases in U.S. adults, according to 2018–2022 CDC data, and is specifically designed for adult use.”
Globally, CAPVAXIVE is approved in the U.S., European Union, Japan, and several other countries. It provides coverage against the serotypes responsible for approximately 84% of invasive pneumococcal disease (IPD) cases in adults ≥50 years, compared with roughly 52% coverage by PCV20, based on CDC ABC data from 2018–2022 (covering ~35 million individuals across 10 U.S. states). Regional variations in serotype prevalence may exist.
Importantly, CAPVAXIVE includes eight unique serotypes not covered by other currently approved pneumococcal vaccines. These serotypes were responsible for roughly 27% of IPD cases in adults ≥50 years and about 30% in adults ≥65 years. While these figures highlight serotype coverage, they do not directly reflect vaccine efficacy, and no head-to-head efficacy studies comparing CAPVAXIVE with PCV20 currently exist.
The systematic review underscores the significant prevalence and resistance patterns associated with CAPVAXIVE-unique serotypes. By covering these serotypes, CAPVAXIVE addresses a substantial portion of PD cases in adults, including those with higher AMR rates, which may inform treatment and prevention strategies.
CAPVAXIVE’s broader coverage, particularly for serotypes 35B and 23A that exhibit high antibiotic resistance, offers potential public health benefits by targeting strains contributing to both invasive disease and non-invasive infections resistant to commonly prescribed antibiotics.
References: CDC Active Bacterial Core Surveillance (ABC) reports, 2018–2023; 15 U.S.-based peer-reviewed studies published between 2015–2025.
