A Phase 3 Randomized Trial Investigating the Safety, Tolerability, and Immunogenicity of V116, an Adult-Specific Pneumococcal Vaccine, Compared with PPSV23, in Adults ≥50 Years of Age (STRIDE-10)

<b>Background</b>: V116 is a 21-valent pneumococcal conjugate vaccine (PCV) designed for adults. It contains the most prevalent serotypes associated with invasive pneumococcal disease (IPD) in adults in regions with established pediatric vaccination programs. This Phase 3 study compared the safety, tolerability, and immunogenicity of V116 with 23-valent pneumococcal polysaccharide vaccine (PPSV23) in adults ≥50 years of age. <b>Methods</b>: In this randomized, active comparator-controlled, parallel-group, multisite, double-blind study, participants were randomized 1:1 to receive a single dose of V116 or PPSV23 (NCT05569954). Primary immunogenicity outcomes assessed the opsonophagocytic activity (OPA) responses for (i) non-inferiority for 12 serotypes common to V116 and PPSV23 based on V116/PPSV23 geometric mean titers (GMTs) at Day 30, and (ii) superiority for nine serotypes unique to V116 using V116/PPSV23 GMTs and the proportions of participants with a ≥4-fold rise in OPA responses from baseline to 30 days post-vaccination. The primary safety outcome was evaluated as the proportion of participants with solicited injection-site and systemic adverse events through Day 5 post-vaccination, and vaccine-related serious adverse events up to 6 months post-vaccination. <b>Findings</b>: V116 was non-inferior to PPSV23 for all 12 common serotypes, superior to PPSV23 for all nine unique serotypes based on V116/PPSV23 GMTs, and superior to PPSV23 for eight of the nine serotypes unique to V116, based on the proportion of participants with a ≥4-fold rise in OPA responses (except for serotype 15C). The safety profile of V116 was comparable to that of PPSV23. <b>Interpretation</b>: In regions with established vaccination programs, V116 could broaden the serotype coverage for residual pneumococcal disease in adults.