Pneumococcal 21-valent conjugate vaccine demonstrates immune response in children 2 to <18 years | Image Credit: © Alernon77 - © Alernon77 - stock.adobe.com.

Positive results related to safety, tolerability, and immunogenicity for Merck's Pneumococcal 21-valent Conjugate Vaccine (CAPVAXIVE) were announced by the manufacturer among children aged 2 to younger than 18 years.¹

According to a press release sent on September 11, 2025, results were from the phase 3 STRIDE-13 trial (NCT06177912) and presented at the European Society of Clinical Microbiology and Infectious Diseases Conference on Vaccines in Lisbon, Portugal.^1,2

The trial, which as of March 2025 had an enrollment of 882 participants, demonstrated that the vaccine elicited immune responses to all 21 serotypes, as assessed by serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs) at 30 days post-vaccination (secondary immunogenicity endpoint).^1,2

Pneumococcal 21-valent Conjugate Vaccine was noninferior to PPSV23 (Pneumovax23) for the 12 serotypes shared between the vaccines (lower bound of the two-sided 95% confidence interval for the serotype-specific OPA GMT ratio >0.5). The vaccine demonstrated superiority to PPSV23 for each of the 9 serotypes included in Pneumococcal 21-valent Conjugate Vaccine, but not PPSV23 (lower bound of the two-sided 95% confidence interval for the serotype-specific OPA GMT ratio >2.0), as measured by serotype-specific OPA GMTs at 30 days post-vaccination.

According to Merck, the proportions of participants with adverse events (AEs) that included systemic and serious vaccine-related AEs, were "generally comparable between groups (primary safety endpoint)." The company reported that solicited injection-site AEs were higher in the Pneumococcal 21-valent Conjugate Vaccine group (72.3%) compared to the PPSV23 group (58.2%).

"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, chief, Pediatric Infectious Diseases, Rambam Health Care Campus; investigator, STRIDE-13 trial. "Results from STRIDE-13 demonstrate the potential of [Pneumococcal 21-valent Conjugate Vaccine] 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," added Lapidot.

Current indications for Pneumococcal 21-valent Conjugate Vaccine

The 21-valent pneumococcal conjugate vaccine is currently indicated for active immunization to prevent invasive disease and pneumonia in adults aged 18 years and older.

Specifically, the vaccine is indicated for:

• Active immunization for the prevention of 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 individuals 18 years of age and older
• Active immunization for the prevention of pneumonia caused by ^{S. pneumoniae} serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F and 35B in individuals 18 years of age and older.

"While [Pneumococcal 21-valent Conjugate Vaccine] was designed to specifically cover the serotypes that cause the majority of invasive pneumococcal disease (IPD) 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, in a statement. Annunziato is the senior vice president of infectious diseases and vaccines, Global Clinic Development at 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," Annunziato added.

Merck added that these data points represented the final readout of the phase 3 STRIDE clinical program, and will be shared with global regulatory authorities, but did not provide a specific timeline.

References:

1. Results from the phase 3 STRIDE-13 trial presented at 6th ESCMID conference on Vaccines. Merck. Press release. Published September 11, 2025. Accessed September 11, 2025. https://www.merck.com/news/capvaxive-pneumococcal-21-valent-conjugate-vaccine-demonstrates-positive-immune-responses-in-children-and-adolescents-at-increased-risk-of-pneumococcal-disease/
2. A clinical study of the V116 vaccine for children and teenagers (V116-013) (STRIDE-13). Clinicaltrials.gov. Updated March 24, 2025. Accessed September 11, 2025. https://clinicaltrials.gov/study/NCT06177912?intr=v116&rank=1