Merck's CAPVAXIVE, a 21-valent pneumococcal conjugate vaccine, is showing promising results in protecting adults against pneumococcal disease. Recent data from the STRIDE-8 Phase 3 trial, presented at IDWeek 2024, highlight the vaccine's ability to elicit robust immune responses in adults, especially those with chronic conditions that elevate their risk. The FDA approved vaccine targets 21 serotypes of Streptococcus pneumoniae, the bacteria responsible for pneumococcal disease, offering a potentially broader shield than existing vaccines.
Immunogenicity and Safety
The STRIDE-8 trial compared CAPVAXIVE to the pneumococcal 15-valent conjugate vaccine (PCV15) followed by the pneumococcal 23-valent polysaccharide vaccine (PPSV23) in vaccine-naive adults aged 18-64 with chronic conditions. The results demonstrated that CAPVAXIVE was immunogenic for all 21 serotypes included in the vaccine, as measured by serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs) and immunoglobulin G (IgG) geometric mean concentrations (GMCs) at Day 30.
Notably, the immune responses elicited by CAPVAXIVE were comparable to PCV15 followed by PPSV23 for the 13 common serotypes and higher for the eight serotypes unique to CAPVAXIVE. Furthermore, the proportion of participants experiencing adverse events (AEs) was numerically lower in the CAPVAXIVE group compared to the PCV15 + PPSV23 group, suggesting a favorable safety profile.
Addressing Unmet Needs
According to Dr. Walter Orenstein, professor emeritus at Emory University and member of Merck’s Scientific Advisory Committee, adults with chronic conditions are particularly vulnerable to invasive pneumococcal disease. The data from STRIDE-8 indicates that CAPVAXIVE's broad serotype coverage can help prevent invasive disease among these vulnerable adults.
CAPVAXIVE is designed to address Streptococcus pneumoniae serotypes predominantly responsible for adult invasive pneumococcal disease (IPD). According to CDC data from 2018-2021, the serotypes covered by CAPVAXIVE are responsible for more cases of IPD in adults compared to PCV20. Specifically, CAPVAXIVE covers serotypes responsible for approximately 84% of IPD cases in adults 50 years and older, compared to approximately 52% covered by PCV20. In adults 65 years and older, CAPVAXIVE covers approximately 85% of IPD cases, while PCV20 covers approximately 51%.
Impact on Disease Burden
Data from a modeling study evaluating the health impact of CAPVAXIVE introduction in U.S. adults were also presented. The study concluded that CAPVAXIVE use reduced IPD incidence by 33.9% in the U.S. after 10 years, assuming continued pediatric PCV vaccination. This equated to approximately 14,000 fewer cases with CAPVAXIVE than PCV20 after 10 years.
Merck's Commitment
Merck has been dedicated to pneumococcal disease prevention through vaccination for over four decades. Paula Annunziato, Senior Vice President of Infectious Diseases and Vaccines at Merck, emphasized the company's commitment to developing vaccines tailored to specific populations, moving away from a one-size-fits-all approach. This dedication is reflected in the design of CAPVAXIVE, which specifically targets the serotypes most prevalent in adult pneumococcal disease.
Disparities in Pneumococcal Disease
In addition to the clinical trial data, Merck presented results from a targeted literature review highlighting disparities in pneumococcal disease burden. The review found that Black adults and those in rural areas with lower education and income face higher disease burden and lower vaccination rates. This underscores the importance of improving equitable access to pneumococcal vaccines like CAPVAXIVE.
Looking Ahead
CAPVAXIVE represents a significant advancement in the prevention of pneumococcal disease in adults. Its broad serotype coverage, favorable safety profile, and potential to reduce disease burden make it a valuable tool for protecting vulnerable populations. As Merck continues to develop and refine its vaccine pipeline, the future looks promising for further reducing the impact of pneumococcal disease worldwide.
