title: Nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants: a longitudinal study.
abstract: BACKGROUND
  To prepare for national introduction of a pneumococcal conjugate vaccine of restricted valency, we studied nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants.
  
  
  METHODS
  We studied 236 infants in 21 villages. We collected nasopharyngeal swab samples at birth, twice per month for 6 months, and every second month until 1 year of age. We studied time to acquisition and duration of pneumococcal carriage according to serotype.
  
  
  RESULTS
  All infants carried S. pneumoniae at some point. Sixty-five serotypes were found, and the 5 most common serotypes (6B, 19F, 6A, 14, and 23F) accounted for 51% of isolates. The mean age at first acquisition of carriage was 33 days (95% confidence interval, 29-36 days). There were no significant differences in acquisition rates between the 6 most common serotypes (P = .067) or between vaccine serotypes, vaccine-related serotypes, or nonvaccine serotypes (P = .317). However, the duration of carriage differed significantly between the 6 most common serotypes (P = .004). The rate of reacquisition of carriage and the duration of carriage did not differ significantly between the 6 most common serotypes (P = .229 and P = .669 respectively). However, nonvaccine types were acquired faster (P = .004) and were carried for a shorter duration (P < .001) than were vaccine serotypes. A previous episode of serotype 14 carriage was associated with delayed reacquisition of this serotype (P = .005) and longer duration of carriage (P = .017).
  
  
  CONCLUSIONS
  The data provided in this study regarding time to acquisition and duration of pneumococcal carriage in Gambian infants provide an important baseline for evaluating the impact of the introduction of a pneumococcal conjugate vaccine in The Gambia and elsewhere in Africa.
authors.affiliation: Bacterial Diseases Programme, MRC Laboratories, Banjul, The Gambia. pandmhill@hotmail.com
authors.forename: Philip C
authors.initials: PC
authors.lastname: Hill
authors.forename: Yin Bun
authors.initials: YB
authors.lastname: Cheung
authors.forename: Abiodun
authors.initials: A
authors.lastname: Akisanya
authors.forename: Kawsu
authors.initials: K
authors.lastname: Sankareh
authors.forename: George
authors.initials: G
authors.lastname: Lahai
authors.forename: Brian M
authors.initials: BM
authors.lastname: Greenwood
authors.forename: Richard A
authors.initials: RA
authors.lastname: Adegbola
mesh_terms: D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology; D012424:Rural Population; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000302:isolation & purification*