Scientific Reports (Apr 2022)

Pneumococcal carriage in unvaccinated children at the time of vaccine implementation into the national immunization program in Poland

  • Izabela Wróbel-Pawelczyk,
  • Patrycja Ronkiewicz,
  • Monika Wanke-Rytt,
  • Dominika Rykowska,
  • Aneta Górska-Kot,
  • Katarzyna Włodkowska,
  • Agnieszka Topczewska-Cabanek,
  • Teresa Jackowska,
  • Joanna Chruszcz,
  • Walentyna Marchut,
  • Agnieszka Mastalerz-Migas,
  • Krzysztof Korzeniewski,
  • GIL Study Team,
  • Anna Skoczyńska,
  • Krzysztof Trzciński

DOI
https://doi.org/10.1038/s41598-022-09488-z
Journal volume & issue
Vol. 12, no. 1
pp. 1 – 11

Abstract

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Abstract We investigated pneumococcal carriage among unvaccinated children under five years of age at a time when the conjugate polysaccharide vaccine (PCV) was introduced in Poland into the national immunization program (NIP). Paired nasopharyngeal swab (NPS) and saliva samples collected between 2016 and 2020 from n = 394 children were tested with conventional culture and using qPCR. The carriage rate detected by culture was 25.4% (97 of 394), by qPCR 39.1% (155 of 394), and 40.1% (158 of 394) overall. The risk of carriage was significantly elevated among day care center attendees, and during autumn/winter months. Among isolates cultured, the most common serotypes were: 23A, 6B, 15BC, 10A, 11A. The coverage of PCV10 and PCV13 was 23.2% (23 of 99) and 26.3% (26 of 99), respectively. Application of qPCR lead to detection of 168 serotype carriage events, with serogroups 15, 6, 9 and serotype 23A most commonly detected. Although the highest number of carriers was identified by testing NPS with qPCR, saliva significantly contributed to the overall number of detected carriers. Co-carriage of multiple serotypes was detected in 25.3% (40 of 158) of carriers. The results of this study represent a baseline for the future surveillance of effects of pneumococcal vaccines in NIP in Poland.