Safety and Immunogenicity of 20-Valent PCV According to Number and Timing of Primary Series Doses

ABSTRACT Background The number and timing of pneumococcal conjugate vaccine (PCV) primary doses can impact infant immune responses. This descriptive post hoc analysis evaluates the immunogenicity of the 20-valent PCV (PCV20) by vaccination timing in healthy infants in 2 key phase 3 trials. Methods Immunogenicity endpoints from study B7471012 comparing PCV20 to 13-valent PCV (PCV13) in a 2+1 schedule were examined by timing of vaccination subgroup; the 2,4m subgroup (participants vaccinated at 2, 4, and 11–12 months of age), and the 3,5m subgroup (participants vaccinated at 3, 5, and 11–12 months). Additionally, immune responses from the 2+1 schedule were compared descriptively with those in study B7471011, in which participants received PCV20 or PCV13 in a 3+1 schedule at ∼2, 4, 6, and 12−15 months. Results Serotype-specific serum immunoglobulin G (IgG) responses in the PCV20 3,5m subgroup were higher than those in the 2,4m subgroup across all 20 vaccine serotypes and comparable to PCV13 immune responses in the 2,4m subgroup. Regardless of primary doses timing, PCV20 2+1 elicited strong immune responses after the toddler dose leading to post-toddler dose IgG levels similar to a 3+1 schedule. PCV20 was safe and well tolerated in both the 2,4m and 3,5 m subgroups. Conclusions In this descriptive analysis of the 2+1 schedule, a 1-month delay in PCV20 priming to 3 and 5 months was associated with improved immune responses comparable with those of PCV13 at 2 and 4 months. NCT04546425 ; NCT04382326 .