Merck, known as MSD outside the United States and Canada, has reported positive results from its Phase 3 STRIDE-13 trial evaluating Capvaxive, its 21-valent pneumococcal conjugate vaccine. The findings, presented at the 6th European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Conference on Vaccines in Lisbon, assessed the vaccine’s safety, tolerability, and immunogenicity in children and adolescents aged 2 to under 18 years who had completed a primary pediatric pneumococcal vaccination regimen and were living with chronic medical conditions that increase their risk of pneumococcal disease.

Results showed that Capvaxive elicited immune responses against all 21 serotypes tested, was noninferior to PPSV23 for the 12 serotypes shared between the two vaccines, and superior for the nine serotypes unique to Capvaxive. Adverse events, including systemic and serious vaccine-related events, were generally comparable between the two groups, with slightly higher injection-site reactions in the Capvaxive arm.

According to Dr. Rotem Lapidot, chief of pediatric infectious diseases at Rambam Health Care Campus and investigator in the trial, children and adolescents with chronic conditions are particularly vulnerable to pneumococcal disease, and broader protection is essential.

The STRIDE-13 trial highlights the potential of Capvaxive to extend coverage by targeting serotypes not addressed in other pediatric regimens. Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines at Merck Research Laboratories, emphasized that while Capvaxive was originally designed for adults, the data demonstrate its added value for younger, at-risk populations.

Capvaxive is already approved in the United States, European Union, Japan, and several other markets for use in adults 18 years and older, where it provides coverage against serotypes responsible for approximately 84% of invasive pneumococcal disease cases in adults over 50, compared with about 52% covered by PCV20.

In children and adolescents with elevated risk, Capvaxive could provide protection for nearly 78% of cases, including 11 unique serotypes that account for roughly 34% of invasive pneumococcal disease cases, based on CDC data. With the final readout of the STRIDE-13 program now available, Merck plans to share the results with regulatory authorities worldwide to potentially expand the indication of Capvaxive for pediatric populations.