Persistence of IgG antibody following routine XXXX immunization with the 7-valent pneumococcal conjugate vaccine.

@entity1 @entity1485
BACKGROUND: Pneumococcal conjugate vaccine ( @entity1485 ) induces protective anticapsular IgG, which mediates disease immunity. IgG persistence may influence long-term protection. METHODS: An observational, prospective, longitudinal study of nasopharyngeal carriage among American Indian households from 2006 to 2008 evaluated long-term immunogenicity of 7-valent @entity1485 (PCV7). @entity1 unimmunized with @entity1485 were age-matched to those PCV7 immunized at least 4 years prior (ratio 1:3 or 1:4). Blood collected at the final study visit was analyzed for PCV7 serotype IgG (enzyme-linked immunosorbent assay) and for functional activity (multiplex-opsonophagocytic assay) for serotypes 4, 6B, 14 and 23F. Geometric mean concentrations (GMCs), titers (GMTs) and the odds of serotype-specific IgG >= 0.35  g/mL were compared according to immunization status using a matched regression approach. RESULTS: Eight unimmunized and 28 immunized @entity1 age-matched at the time of serum collection (mean age: 7.9 years) were included. Serotype-specific GMCs, GMTs and proportions above the correlate of protection did not differ between the groups except for serotypes 14 and 23F. Serotype 14 GMCs (immunized 0.7 vs. unimmunized 0.2; P = 0.02) and serotype 23F GMTs (immunized 388.3 vs. unimmunized 47.8; P = 0.03) were significantly higher among immunized children. IgG concentrations and functional titers among immunized @entity1 were strongly correlated for serotypes 4 (r = 0.78; P  <= 0.001) and 14 (r = 0.52; P  <= 0.01). CONCLUSIONS: @entity1485 serotype-specific IgG concentrations 4 years following @entity1485 vaccination do not persist above natural levels for most serotypes. Exposure to pneumococcus may be critical in maintaining persistent serotype-specific IgG; the elimination of circulating vaccine type pneumococci by @entity1485 may have effects on long-term immunity.
