Merck announced the FDA has expanded the indication for the company’s Pneumococcal 21-valent Conjugate Vaccine (Capvaxive) to include children and adolescents aged 2 to 17 years who have completed a primary pneumococcal vaccination series and have underlying chronic medical conditions that increase their risk of pneumococcal disease.
The approval makes Capvaxive the only pneumococcal conjugate vaccine in the United States specifically studied and indicated for this at-risk pediatric population.
Phase 3 STRIDE-13 Trial Supports Expanded Pediatric Indication
The FDA's decision was supported by findings from the phase 3 STRIDE-13 study, a randomized, double-blind, active comparator-controlled trial that enrolled 874 children and adolescents aged 2 to 17 years with chronic conditions known to increase the risk of pneumococcal disease, including diabetes, chronic heart disease, chronic kidney disease, chronic liver disease, and chronic lung disease.
Participants who had previously completed a primary pneumococcal vaccination series were randomized to receive a single dose of either Capvaxive (n=527) or PPSV23 (n=347). Investigators found that Capvaxive met noninferiority criteria for all 12 serotypes shared with PPSV23 and generated significantly greater opsonophagocytic activity geometric mean titers (OPA GMTs) against the nine serotypes unique to Capvaxive.
The vaccine also elicited immune responses against serotype 15B, which is cross-reactive with serotype 15C. Safety findings were generally comparable between the two vaccine groups, with most adverse reactions resolving within three days. Serious adverse events occurred in 5.5% of Capvaxive recipients and 7.2% of PPSV23 recipients, with no meaningful safety imbalances observed.
"Children and adolescents with certain chronic conditions are at an increased risk for pneumococcal disease, including pneumonia, meningitis, and bloodstream infections," Rotem Lapidot, MD, chief of pediatric infectious diseases at Rambam Health Care Campus and a STRIDE-13 investigator, said in a statement. "This approval recognizes the potential of Capvaxive to deliver additional protection by including serotypes not contained in approved primary pediatric PCV series."
What You Need to Know
Capvaxive is now the only pneumococcal conjugate vaccine specifically studied and indicated in the U.S. for children and adolescents aged 2 to 17 years at increased risk for pneumococcal disease.
In the phase 3 STRIDE-13 trial, the vaccine demonstrated noninferior immune responses to PPSV23 for shared serotypes and significantly higher responses against the nine serotypes unique to Capvaxive.
The vaccine may provide broader protection for high-risk pediatric patients by targeting additional pneumococcal serotypes not included in currently approved pediatric PCV series.
Vaccine Offers Expanded Serotype Coverage for High-Risk Patients
Capvaxive is Merck's 21-valent pneumococcal conjugate vaccine designed to target pneumococcal serotypes responsible for a substantial proportion of invasive pneumococcal disease (IPD). The vaccine includes eight serotypes not found in other approved pneumococcal conjugate vaccines: 15A, 15C, 16F, 23A, 23B, 24F, 31, and 35B.
According to Merck, a 2025 analysis of CDC Active Bacterial Core surveillance data found that Capvaxive's serotypes accounted for approximately 79% of IPD cases among children with risk conditions. The vaccine's 11 unique serotypes were responsible for roughly 40% of cases in this population.
Previously approved for adults aged 18 years and older, Capvaxive is now indicated for the prevention of invasive pneumococcal disease in at-risk children and adolescents aged 2 through 17 years who have completed a primary pneumococcal vaccination series. The vaccine is administered as a single dose and is intended to complement—not replace—existing pediatric pneumococcal vaccination schedules.
"While Capvaxive was specifically designed for adults, it may also offer additional disease protection for this specific population of children and adolescents, when given after the primary pediatric pneumococcal vaccination series," Paula Annunziato, MD, senior vice president of infectious diseases and vaccines, global clinical development at Merck Research Laboratories, said in a statement. "The approval of Capvaxive for children and adolescents at increased risk for pneumococcal disease demonstrates our commitment to addressing this disease in people of all ages."
