Indirect Comparison of PCV20 Immunogenicity with PCV10 in Pediatric 3 + 1 and 2 + 1 Schedules.

Introduction: The 20-valent pneumococcal conjugate vaccine (PCV20) was licensed for prevention of pneumococcal disease in infants and children on the basis of immunogenicity compared with PCV13. We aimed to evaluate PCV20 immunogenicity compared with PCV10 (Synflorix; PhiD-CV) because both vaccines demonstrated lower immunogenicity than PCV13. Nevertheless, PCV10 was highly effective against vaccine-serotype pneumococcal disease in post-licensure studies. Since no study has directly compared PCV20 versus PCV10, we conducted an indirect comparison.

Methods: We conducted indirect comparisons for PCV20 versus PCV10 using data from published randomized control trials that directly compared these vaccines with PCV13 in 3 + 1 or 2 + 1 schedules. Serotype-specific immunoglobulin (Ig)G concentrations and opsonophagocytic activity (OPA) were assessed post-booster dose and post-primary series. First, geometric mean ratios (GMRs) were obtained for shared serotypes for each direct comparison against PCV13; we conducted a meta-analysis to generate pooled GMRs if data from multiple trials were available. Next, we indirectly compared relative GMRs of PCV20 versus PCV10 using PCV13 as the common comparator. In this descriptive analysis, GMRs > 1 favored PCV20 and GMR < 1 favored PCV10.

Results: Meta-analyses of PCV10 versus PCV13 data found that PCV10 was less immunogenic for most of the ten shared serotypes. When indirectly compared via PCV13, the relative immunogenicity of PCV20 versus PCV10 varied by serotype. Overall, IgG responses for the ten shared serotypes were similar for both 3 + 1 and 2 + 1 schedules, both post-primary series and post-booster dose. GMRs for both IgG and OPA were close to the line of equivalence, or spread between favoring PCV20 or PCV10.

Conclusions: The comparable immunogenicity of PCV20 versus PCV10 in 2 + 1 and 3 + 1 schedules suggests that PCV20 will have similar effectiveness for the ten serotypes included in both vaccines, including for direct protection during infancy and toddler age, while also expanding serotype coverage. Effectiveness for PCV20 needs to be confirmed in post-marketing studies.