Pneumococcal Carriage in Sub-Saharan Africa—A Systematic Review

Effua Usuf,Richard A Adegbola,Andrew Hall,Christian Bottomley,Caroline L Trotter

doi:10.1371/journal.pone.0085001

Abstract

BackgroundPneumococcal epidemiology varies geographically and few data are available from the African continent. We assess pneumococcal carriage from studies conducted in sub-Saharan Africa (sSA) before and after the pneumococcal conjugate vaccine (PCV) era.MethodsA search for pneumococcal carriage studies published before 2012 was conducted to describe carriage in sSA. The review also describes pneumococcal serotypes and assesses the impact of vaccination on carriage in this region.ResultsFifty-seven studies were included in this review with the majority (40.3%) from South Africa. There was considerable variability in the prevalence of carriage between studies (I-squared statistic = 99%). Carriage was higher in children and decreased with increasing age, 63.2% (95% CI: 55.6–70.8) in children less than 5 years, 42.6% (95% CI: 29.9–55.4) in children 5–15 years and 28.0% (95% CI: 19.0–37.0) in adults older than 15 years. There was no difference in the prevalence of carriage between males and females in 9/11 studies. Serotypes 19F, 6B, 6A, 14 and 23F were the five most common isolates. A meta-analysis of four randomized trials of PCV vaccination in children aged 9–24 months showed that carriage of vaccine type (VT) serotypes decreased with PCV vaccination; however, overall carriage remained the same because of a concomitant increase in non-vaccine type (NVT) serotypes.ConclusionPneumococcal carriage is generally high in the African continent, particularly in young children. The five most common serotypes in sSA are among the top seven serotypes that cause invasive pneumococcal disease in children globally. These serotypes are covered by the two PCVs recommended for routine childhood immunization by the WHO. The distribution of serotypes found in the nasopharynx is altered by PCV vaccination.

Highlights

The human nasopharynx is the main reservoir for pneumococci
The bacteria which adhere to pharyngeal epithelial cells through epithelial receptor molecules may be acquired very early in life [1,2], and in most children the pneumococcus is present in the nasopharynx at some point in the first few years of life [3]
The search was conducted in December 2011 using the electronic databases MEDLINE, EMBASE and African Index Medicus (AIM)

Summary

Introduction

The human nasopharynx is the main reservoir for pneumococci. The bacteria which adhere to pharyngeal epithelial cells through epithelial receptor molecules may be acquired very early in life [1,2], and in most children the pneumococcus is present in the nasopharynx at some point in the first few years of life [3]. Carriage is generally higher in developing countries and among economically deprived populations [4,5]. The prevalence of carriage might vary between developing countries. Abdullahi et al suggested that colonisation prevalence in East and Southern Africa is substantially lower than in the Gambia [6]. We assess pneumococcal carriage from studies conducted in sub-Saharan Africa (sSA) before and after the pneumococcal conjugate vaccine (PCV) era

Methods

Results

Conclusion