Pneumococcal Carriage in Sub-Saharan Africa—A Systematic Review

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.

Pneumococcal Carriage in Children under Five Years in Uganda-Will Present Pneumococcal Conjugate Vaccines Be Appropriate?

“…In a systematic review on pneumococcal carriage in Sub-Saharan Africa[10], carriage rates varied widely between 21–94%, but in the meta-analysis used, carriage rates (63%) were similar to those in our study.…”

“…A range of 35–93% of healthy children aged under five years in low-income countries has been shown to be colonized with pneumococci in the nasopharynx [9,10]. Pneumococcal conjugate vaccine (PCV) reduces vaccine-type pneumococcal carriage and thereby the dynamics of serotype transmission and pneumococcal disease [11].…”

Carriage of Streptococcus pneumoniae and Other Respiratory Bacterial Pathogens in Low and Lower-Middle Income Countries: A Systematic Review and Meta-Analysis

“…In addition, we did not include upper-middle income countries in the analysis even though some populations within these countries may share characteristics with populations in low or lower-middle income countries. For instance, in one study in South Africa, prevalence of pneumococcal carriage was high (22.5%–61.0%) in children younger than five years of age [112], whereas a study in Costa Rica showed that infants acquire nasopharyngeal carriage of S. pneumoniae at a rate (3.1% at one month of age and 19.4% at one year of age) comparable to that seen in developed countries [113].…”

The Efficacy and Duration of Protection of Pneumococcal Conjugate Vaccines Against Nasopharyngeal Carriage

“…Three were PCV9 trials 29,32,37 and 1 was a PCV10 trial. 26,27 We were unable to restrict the latter to PCV7 serotypes only (as all data for PCV10 serotype were aggregated), and we explored the sensitivity of our model output to including (or not) data from that study. Nine data points were from surveys after booster vaccination (Table 1).…”

“…Finally, overall and booster schedule VE C estimates and respective model coefficients were similar with and without data from the PCV10 trial. 26,27 We explored 2 other models of waning, in addition to the main model (Appendix, Supplemental Digital Content 2, http:// links.lww.com/INF/C159). In all 3 models, there was good evidence of protective efficacy in the first few years after vaccination.…”