Age-stratified prevalences of pneumococcal-serotype-specific immunoglobulin G in England and their relationship to the serotype-specific incidence of invasive pneumococcal disease prior to the introduction of the pneumococcal 7-valent conjugate vaccine

Abstract

Recent changes to the childhood immunization schedule in the United Kingdom have resulted in the inclusion of the 7-valent pneumococcal conjugate vaccine. However, the seroprevalence of pneumococcal antibodies in the population was unknown. To address this, we measured pneumococcal, age-specific immunoglobulin G (IgG) concentrations specific for nine serotypes by an assay run on the Bioplex platform, using 2,664 serum samples collected in England from 2000 to 2004. The lowest concentrations of IgG specific to all serotypes and the proportions of serotype-specific IgG concentrations of >/=0.35 microg/ml were observed in children aged <1 year. From 1 year on, there was a general increase in antibody levels with increasing age, and they remained high in adults. Maternal antibody was detected in young children aged <36 days but waned rapidly. Comparison of the age-specific seroprevalence of serotype-specific IgG to the serotype-specific incidence of invasive pneumococcal disease demonstrated a general inverse relationship for all age groups except the elderly. These data provide a baseline for natural immunity to the pneumococcal serotypes analyzed prior to the introduction of pneumococcal conjugate vaccine in the United Kingdom.

FIG. 1.

Age-specific pneumococcal serotype-specific IgG GMC (±95% CI) in England from 2000 to 2004. The y axis scales are different for each of the individual serotypes.

FIG. 1.

Age-specific pneumococcal serotype-specific IgG GMC (±95% CI) in England from 2000 to 2004. The y axis scales are different for each of the individual serotypes.

FIG. 2.

Age-specific incidence of laboratory-confirmed IPD in England from 2000 to 2004 (dashed gray line) and prevalence of serotype-specific IgG at concentrations of ≥0.35 μg/ml (solid black line). The incidence rates of IPD for individual serotypes are expressed on different scales. No incidence of IPD due to serotype 5 was confirmed from 2000 to 2005.

FIG. 2.

Age-specific incidence of laboratory-confirmed IPD in England from 2000 to 2004 (dashed gray line) and prevalence of serotype-specific IgG at concentrations of ≥0.35 μg/ml (solid black line). The incidence rates of IPD for individual serotypes are expressed on different scales. No incidence of IPD due to serotype 5 was confirmed from 2000 to 2005.