A cross-sectional observational study of pneumococcal carriage in children, their parents, and older adults following the introduction of the 7-valent pneumococcal conjugate vaccine

Abstract

Using nasopharyngeal carriage as a marker of vaccine impact, pneumococcal colonization and its relation to invasive disease were examined in children, their parents, and older adults in the United Kingdom following introduction of 7-valent pneumococcal conjugate vaccine (PCV7) and prior to 13-valent pneumococcal conjugate vaccine (PCV13).A cross-sectional observational study was conducted, collecting nasopharyngeal swabs from children aged 25 to 55 months who had previously received 3 doses of PCV7, their parents, and adults aged ≥65 years. Pneumococcal serotyping was conducted according to World Health Organization guidelines with nontypeable isolates further analyzed by molecular serotyping. A national invasive disease surveillance program was conducted throughout the corresponding period.Pneumococcus was isolated from 47% of children, 9% of parents, and 2.2% of older adults. For these groups, the percentage of serotypes covered by PCV7 were 1.5%, 0.0%, and 15.4%, with a further 20.1%, 44.4%, and 7.7% coverage added by those in PCV13. In each group, the percentage of disease due to serotypes covered by PCV7 were 1.0%, 7.4% and 5.1% with a further 65.3%, 42.1%, and 61.4% attributed to those in PCV13.The prevalence of carriage is the highest in children, with direct vaccine impact exemplified by low carriage and disease prevalence of PCV7 serotypes in vaccinated children, whereas the indirect effects of herd protection are implied by similar observations in unvaccinated parents and older adults.

FIGURE 1

Total proportion of nasopharyngeal swabs from children (aged 25–55 months), their parents, and older adults (aged ≥65 years), collected between November 2010 and September 2011, which had pneumococcus identified (A). (Bars indicate 95% CI). These were then categorized according to whether the serotype was covered by the PCVs PCV7 and PCV13 or was a NVT (B). IPD isolates from across England and Wales for children, adults, and older adults, and across the corresponding time period, were serotyped by Public Health England and categorized according to whether the serotype was covered by the PCVs PCV7 and PCV13 or was a NVT (C). CI = confidence interval, IPD = invasive pneumococcal disease, NVT = nonvaccine type, PCV13 = 13-valent pneumococcal conjugate vaccine, PCV7 = 7-valent pneumococcal conjugate vaccine.

FIGURE 2

The proportion of nasopharyngeal pneumococcal carriage by each identified serotype in PCV7-vaccinated children aged 25 to 55 months (A), their parents (B), and older adults (C) collected between November 2010 and September 2011 (bars), and the proportion of IPD in England and Wales, identified by Public Health England, over the corresponding time period (diamonds). IPD = invasive pneumococcal disease, NT = nontypeable, PCV7 = 7-valent pneumococcal conjugate vaccine.

FIGURE 3

The invasive disease potential expressed as an odds ratio with 95% CI for serotypes covered by PCV13 were calculated and represented against the proportion of nasopharyngeal carriage in the preschool children age group. The size of the marker is relative to the ranking of the serotype's OR weighting. Serotypes 4, 5, 6A, 9V, 14, and 18C were not isolated from the nasopharynx, whereas serotype 23F did not cause disease in any children and hence is not represented. CI = confidence interval, OR = odds ratio, PCV13 = 13-valent pneumococcal conjugate vaccine.