Pneumococcal carriage in sub-Saharan Africa--a systematic review.
BACKGROUND
Pneumococcal 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.


METHODS
A 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.


RESULTS
Fifty-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.


CONCLUSIONS
Pneumococcal 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.
Child Survival, Medical Research Council The Gambia Unit, Fajara, The Gambia.
Effua
E
Usuf
Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Christian
C
Bottomley
GlaxoSmithKline Vaccines, Wavre, Belgium.
Richard A
RA
Adegbola
Faculty of Epidemiology and Public Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Andrew
A
Hall
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D012703:Serotyping; D013019:South Africa / Q000453:epidemiology; D013296:Streptococcus pneumoniae / Q000276:immunology / Q000472:pathogenicity; D018074:Vaccines, Conjugate / Q000627:therapeutic use; D055815:Young Adult
D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate