A systematic review presented at IDWeek 2025 found that pneumococcal serotypes unique to Merck’s 21-valent conjugate vaccine, Capvaxive, are more prevalent among US adults and show higher rates of antibiotic resistance compared to those unique to PCV20.
Findings presented at IDWeek 2025 emphasize the need to target pneumococcal serotypes that disproportionately affect adults and exhibit resistance to commonly prescribed antibiotics. Merck announced results from a systematic review of 15 studies published between 2015 and 2025 assessing the epidemiology and antimicrobial resistance of pneumococcal serotypes covered by Capvaxive (Pneumococcal 21-valent Conjugate Vaccine) in comparison to those covered by PCV20.
The review incorporated US data from published studies and Centers for Disease Control and Prevention (CDC) Active Bacterial Core Surveillance reports. Results showed that Capvaxive-unique serotypes were more common among adults with pneumococcal disease (PD) than those covered solely by PCV20. In particular, Capvaxive-unique serotypes such as 35B and 23A demonstrated notably high resistance to penicillin and erythromycin. Among adults aged 65 and older, invasive pneumococcal disease caused by Capvaxive-unique serotypes accounted for over three times the prevalence of PCV20-unique serotypes.
"By covering the serotypes responsible for the majority of invasive pneumococcal disease cases in US adults, based on 2018-2022 national-level CDC data, Capvaxive is specifically designed for adults," Paula Annunziato, MD, senior vice president of infectious diseases and vaccines at Merck Research Laboratories, said in a statement. Capvaxive is currently approved in the US, European Union, Japan, and other countries.
Capvaxive-unique serotypes are significantly more prevalent among US adults, especially those aged 50 and older, compared to serotypes unique to PCV20.
Several Capvaxive-covered serotypes, notably 35B and 23A, show high resistance to common antibiotics like penicillin and erythromycin.
Capvaxive covers serotypes responsible for approximately 84% of invasive pneumococcal disease cases in adults 50 and older—providing broader adult-specific protection than current vaccines.
Capvaxive is Merck’s 21-valent pneumococcal conjugate vaccine indicated for active immunization for the prevention of invasive disease and pneumonia in adults 18 years of age and older. Capvaxive is specifically designed to help address Streptococcus pneumoniae serotypes predominantly responsible for adult invasive pneumococcal disease (IPD), including eight unique serotypes, 15A, 15C, 16F, 23A, 23B, 24F, 31 and 35B compared to other pneumococcal vaccines. Capvaxive is administered as a single dose.
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