Safety and Immunogenicity of 20-valent Pneumococcal Conjugate Vaccine According to Number and Timing of Primary Series Doses

BACKGROUND: The number and timing of pneumococcal conjugate vaccine (PCV) primary doses can impact infant immune responses. This descriptive post hoc analysis evaluates the 20-valent PCV (PCV20) immunogenicity 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 dosing regimen subgroup: the 2,4m subgroup (vaccinations at 2, 4 and 11-12 months of age) and the 3,5m subgroup (vaccinations 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: In this descriptive analysis, 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 dose timing, PCV20 2 + 1 elicited strong booster immune responses with post-toddler dose IgG levels similar to a 3 + 1 schedule. A stratified analysis showed little evidence of effect modification by maternal Tdap vaccination status. 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 to those of PCV13 at 2 and 4 months.