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. 2012;7(2):e30787.
doi: 10.1371/journal.pone.0030787. Epub 2012 Feb 20.

The prevalence and risk factors for pneumococcal colonization of the nasopharynx among children in Kilifi District, Kenya

Osman Abdullahi  1 , Angela Karani, Caroline C Tigoi, Daisy Mugo, Stella Kungu, Eva Wanjiru, Jane Jomo, Robert Musyimi, Marc Lipsitch, J Anthony G Scott
Affiliations

The prevalence and risk factors for pneumococcal colonization of the nasopharynx among children in Kilifi District, Kenya

Osman Abdullahi et al. PLoS One. 2012.

Abstract

Background: Pneumococcal conjugate vaccines (PCV) reduce nasopharyngeal carriage of vaccine-serotype pneumococci but increase in the carriage of non-vaccine serotypes. We studied the epidemiology of carriage among children 3-59 months old before vaccine introduction in Kilifi, Kenya.

Methods: In a rolling cross-sectional study from October 2006 to December 2008 we approached 3570 healthy children selected at random from the population register of the Kilifi Health and Demographic Surveillance System and 134 HIV-infected children registered at a specialist clinic. A single nasopharyngeal swab was transported in STGG and cultured on gentamicin blood agar. A single colony of pneumococcus was serotyped by Quellung reaction.

Results: Families of 2840 children in the population-based sample and 99 in the HIV-infected sample consented to participate; carriage prevalence was 65.8% (95% CI, 64.0-67.5%) and 76% (95% CI, 66-84%) in the two samples, respectively. Carriage prevalence declined progressively with age from 79% at 6-11 months to 51% at 54-59 months (p<0.0005). Carriage was positively associated with coryza (Odds ratio 2.63, 95%CI 2.12-3.25) and cough (1.55, 95%CI 1.26-1.91) and negatively associated with recent antibiotic use (0.53 95%CI 0.34-0.81). 53 different serotypes were identified and 42% of isolates were of serotypes contained in the 10-valent PCV. Common serotypes declined in prevalence with age while less common serotypes did not.

Conclusion: Carriage prevalence in children was high, serotypes were diverse, and the majority of strains were of serotypes not represented in the 10-valent PCV. Vaccine introduction in Kenya will provide a natural test of virulence for the many circulating non-vaccine serotypes.

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Conflict of interest statement

Competing Interests: Professor Scott has received grant support from GSK and travel/accommodation support to attend a Merck meeting. Professor Lipsitch has been paid for consultancy services by Novartis Vaccines & Diagnostics, Pfizer/Wyeth Vaccines, Avian/Pandemic Flu Registry (Outcome Sciences), i3 Innovus (consulting company that works for pharmas) and AIR (a company developing risk model for pandemic flu). There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1
Figure 1. Prevalence (and 95% CI) of nasopharyngeal carriage in children in Kilifi by age and by calendar month within the survey.
Figure 2
Figure 2. Prevalence of carriage of common and less common pneumococcal serotypes by age.
See this image and copyright information in PMC

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