Persistence of immunity in children immunised with 13-valent pneumococcal conjugate vaccine and impact on nasopharyngeal carriage: a cross-sectional study.

In 500 children aged ≤10 years after 13-valent pneumococcal conjugate vaccine (PCV)13 immunisation in different schedules, serotypes 19A-specific and 19F-specific immunoglobulin G (IgG) were predicted to persist above 0.35 µg/mL for ≥10 years in all groups, likely due to PCV13-induced memory with natural boosting from residual diseases and colonisation. Generally, serotype-specific IgG could persist above 0.35 µg/mL longer (≥5 years) in the catch-up group than in the 2+1 and 3+1 immunisation groups. 14.5% of the carriage isolates belonged to PCV13 serotypes; statistical analysis revealed that a high serum IgG level (>10.96 µg/mL) will be required to eliminate the point-prevalence nasopharyngeal carriage of serotype 19A.