Hyporesponsiveness to the infecting serotype after vaccination of children with seven-valent pneumococcal conjugate vaccine following invasive pneumococcal disease

Abstract Antibody responses to the infecting serotype in children who are vaccinated with pneumococcal conjugate vaccine (PCV) after having invasive pneumococcal diseases (IPD) have not been fully investigated. Of 56 children diagnosed with IPD between October 2009 and April 2013 in whom the infecting serotype was confirmed, 17 who were vaccinated with PCV7 following IPD were tested to determine the geometric mean concentration of serotype-specific immunoglobulin G (IgG) and the geometric mean titers of opsonization indices (OIs) using paired sera obtained at the onset of IPD and after PCV doses following the resolution of IPD. The geometric mean concentrations of serotype-specific IgG for all PCV7 serotypes other than serotype 6B were significantly increased after the last PCV7 dose compared with those at the time of IPD onset ( P  5.0 μg/ml. After the last PCV7 dose, the OIs for the infecting serotype remained n  = 5) and 23F ( n  = 1). No difference was found between the responders ( n  = 8) and the hyporesponders ( n  = 6) with regard to any clinical characteristics. Our data suggest that hyporesponsiveness to the infecting serotype may occur in children vaccinated with PCV7 following IPD.