Indirect comparison of the immunogenicity of 15-valent and 20-valent pneumococcal conjugate vaccines in children using a 2+1 schedule

Clinical trials have compared new pneumococcal conjugative vaccines (PCVs; PCV15 and PCV20) to an established PCV (PCV13) in a routine 2 + 1 schedule. This study performed an indirect comparison of PCV15 vs. PCV20 immune responses in healthy infants and toddlers. Pooled, matching-adjusted PCV15 trials were indirectly compared to the analogous PCV20 trial for IgG response rate difference (RRD) and geometric mean concentration ratio (GMR) at the post-primary series (PPS) and post-toddler dose (PTD) timepoints. At PPS, PCV15 was non-inferior for RRD and GMR as compared to PCV20 for all PCV13 serotypes. Moreover, PCV15 was superior to PCV20 for the RRDs of serotypes 1, 3, 4, 5, 6B, 9V, and 23F and GMRs of serotypes 3, 4, 5, 6B, 9V, and 23F at PPS. At PTD, RRDs were comparable for all PCV13 serotypes, except serotype 3, for which PCV15 was superior. PCV15 was superior for the GMRs of serotypes 3, 6B, and 23F, and comparable for the remaining serotypes at PTD. RRDs for serotypes 22F and 33F were non-inferior at both PPS and PTD. In a 2 + 1 schedule, PCV15 demonstrates immunogenicity comparable or superior to PCV20 across PCV13 serotypes, especially for serotype 3.