By IDSE News Staff
Positive results from the phase 3 STRIDE-13 trial evaluating pneumococcal 21-valent conjugate vaccine (PCV21; Capvaxive, Merck) were presented at the 2025 European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Conference on Vaccines, taking place in Lisbon, Portugal (abstract 00093).
STRIDE-13 (ClinicalTrials.gov Identifier: NCT06177912) is a phase 3, randomized controlled, double-blind, active-comparator clinical trial, studying the safety, tolerability and immunogenicity of PCV21 compared with pneumococcal 23-valent polysaccharide vaccine (PPSV23; Pneumovax 23, Merck) in children and adolescents between 24 months and 17 years ofage who have completed a primary pediatric pneumococcal vaccination regimen and have one or more chronic medical conditions that put them at an increased risk for pneumococcal disease. The comorbidities included diabetes mellitus, chronic compensated liver disease, chronic lung disease, chronic heart disease or chronic kidney disease.
The study enrolled 882 participants who were randomized 3:2 to receive a single dose of PCV21 or PPSV23 following completion of a primary pediatric pneumococcal vaccine regimen, such as PCV7 (pneumococcal 7-valent conjugate vaccine), PCV10 (pneumococcal 10-valent conjugate vaccine) or PCV13 (pneumococcal 13-valent conjugate vaccine).
Immunogenicity of PCV21 serotypes was assessed 30 days post-vaccination by measuring serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs). Safety was evaluated as the proportion of participants with adverse events (AEs). Results demonstrated that:
- PCV21 elicited immune responses to all 21 serotypes (or strains) as assessed by serotype-specific OPA GMTs at 30 days post-vaccination (secondary immunogenicity end point);
- PCV21 was noninferior to PPSV23 for each of the 12 serotypes shared between the vaccines and superior to PPSV23 for each of the nine serotypes unique to PCV21, as measured by serotype-specific OPA GMTs at 30 days post-vaccination (primary immunogenicity end point); and
- proportions of participants with AEs, including systemic and serious vaccine-related AEs, were generally comparable between groups (primary safety end point).
“Children and adolescents living with chronic medical conditions are at increased risk of pneumococcal disease and offering them additional protection is essential,” said Rotem Lapidot, MD, the chief of pediatric infectious diseases at Rambam Health Care Campus, and investigator, STRIDE-13 trial. “Results from STRIDE-13 demonstrate the potential of Capvaxive to deliver protection for these vulnerable populations, who may benefit from additional pneumococcal disease coverage by including serotypes not contained in other approved pneumococcal infant regimens.”
In the United States, PCV21 is indicated for the 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 people 18 years of age and older. The indication was approved under an accelerated approval based on immune responses. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.
“While Capvaxive was designed to specifically cover the serotypes that cause the majority of invasive pneumococcal disease … cases in adults, findings from STRIDE-13 underscore its added potential to help protect children and adolescents who are at an increased risk,” said Paula Annunziato, MD, the senior vice president, infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories. “We are encouraged by the safety and immunogenicity data presented at the 6th ESCMID Conference on Vaccines, which underpin our commitment to ensuring infants and adults have access to protection against invasive pneumococcal disease.”
There are about 100 different serotypes of S. pneumoniae. Pneumococcal pneumonia is the most common clinical presentation of pneumococcal disease in adults. It’s estimated that more than 225,000 adults are hospitalized from pneumococcal pneumonia each year in the United States.
