Carriage of Haemophilus influenzae is associated with pneumococcal vaccination in Italian children

Romina Camilli, Maria Fenicia Vescio, Maria Giufrè, Laura Daprai, Maria Laura Garlaschi, Marina Cerquetti, Annalisa Pantosti

Research output: Contribution to journalArticlepeer-review


Background: The pneumococcal population changes observed after the implementation of children immunization with pneumococcal conjugative vaccines (PCV) might have affected the composition of the microbial flora inhabiting the same ecological niche of Streptococcus pneumoniae. The aim of this study was to investigate the effect of PCV immunization, (PCV7 or PCV13), on S. pneumoniae and Haemophilus influenzae colonization in young children in Italy. Methods: Nasopharyngeal swabs were obtained from 301 children under 6 years of age (vaccinated or unvaccinated with PCV) during the period January-April 2012. Presence of S. pneumoniae and H. influenzae was investigated using conventional cultural methods. S. pneumoniae isolates were serotyped by the Quellung reaction; capsular type of H. influenzae isolates was determined by PCR. The pattern of associations between the two species and potential risk factors were investigated by a Structural Equation Modelling (SEM) analysis. Results: The prevalence of carriage was 31.56% and 43.18% for S. pneumoniae and H. influenzae, respectively. The majority of S. pneumoniae isolates belonged to non vaccine serotypes (non PCV13-types 81.1%) while H. influenzae isolates were all non-typeable. SEM analysis revealed a synergistic association between S. pneumoniae and H. influenzae colonization (rho: 0.27; 95%CI: 0.09-0.46; p=. 0.004). In addition, children vaccinated with PCV, either with PCV7 (coef 0.43; 95%CI: 0.07-0.79; p=. 0.021) or with PCV13 (coef: 0.45; 95%CI: 0.08-0.82; p=. 0.018), were more likely to be colonized by H. influenzae. Conclusions: Pneumococcal vaccination increased H. influenzae nasopharyngeal carriage in children. This result highlights that an indirect effect of PCV vaccination can be perturbation of the nasopharyngeal flora. In the era of higher-valent pneumococcal vaccines, surveillance of carriage is crucial to monitor alterations in the bacterial ecosystem, thus preventing possible clinical problems.

Original languageEnglish
Pages (from-to)4559-4564
Number of pages6
Issue number36
Publication statusPublished - Aug 26 2015


  • Haemophilus influenzae
  • Nasopharyngeal carriage
  • PCV13
  • PCV7
  • Streptococcus pneumoniae

ASJC Scopus subject areas

  • Immunology and Microbiology(all)
  • Infectious Diseases
  • Public Health, Environmental and Occupational Health
  • veterinary(all)
  • Molecular Medicine


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