Longitudinal characterization of nasopharyngeal colonization with Streptococcus pneumoniae in a South African birth cohort post 13-valent pneumococcal conjugate vaccine implementation

Sci Rep. 2018 Aug 21;8(1):12497. doi: 10.1038/s41598-018-30345-5.

Abstract

Monitoring changes in pneumococcal carriage is key to understanding vaccination-induced shifts in the ecology of carriage and impact on health. We longitudinally investigated pneumococcal carriage dynamics in infants. Pneumococcal isolates were obtained from nasopharyngeal (NP) swabs collected 2-weekly from 137 infants enrolled from birth through their first year of life. Pneumococci were serotyped by sequetyping, confirmed by Quellung. Pneumococci were isolated from 54% (1809/3331) of infants. Median time to first acquisition was 63 days. Serotype-specific acquisition rates ranged from 0.01 to 0.88 events/child-year and did not differ between PCV13 and non-PCV13 serotypes (0.11 events/child-year [95% CI 0.07-0.18] vs. 0.11 events/child-year [95% CI 0.06-0.18]). There was no difference in carriage duration between individual PCV13 and non-PCV13 serotypes (40.6 days [95% CI 31.9-49.4] vs. 38.6 days [95% CI 35.1-42.1]), however cumulatively the duration of carriage of non-PCV13 serotypes was greater than PCV13 serotypes (141.2 days (95% CI 126.6-155.8) vs. 30.7 days (95% CI 22.3-39.0). Frequently carried PCV13 serotypes included 19F, 9V, 19A and 6A, while non-PCV13 serotypes included 15B/15C, 21, 10A, 16F, 35B, 9N and 15A. Despite high immunization coverage in our setting, PCV13 serotypes remain in circulation in this cohort, comprising 22% of isolates. Individual PCV13 serotypes were acquired, on average, at equivalent rate to non-PCV13 serotypes, and carried for a similar duration, although the most common non-PCV13 serotypes were more frequently acquired than PCV13 serotypes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier State / diagnosis
  • Carrier State / microbiology
  • Female
  • Humans
  • Infant
  • Longitudinal Studies
  • Male
  • Nasopharynx / microbiology*
  • Pneumococcal Vaccines / administration & dosage*
  • Pneumococcal Vaccines / immunology
  • Serogroup
  • Streptococcus pneumoniae / immunology*
  • Vaccines, Conjugate / administration & dosage*
  • Vaccines, Conjugate / immunology

Substances

  • Pneumococcal Vaccines
  • Vaccines, Conjugate