Pneumococcal Carriage in Gambian Infants

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 ( ) or between vaccine serotypes, vaccine-related serotypes, P p .067 or nonvaccine serotypes ( ). However, the duration of carriage differed significantly between the 6 most P p .317 common serotypes ( ). The rate of reacquisition of carriage and the duration of carriage did not differ P p .004 significantly between the 6 most common serotypes ( and respectively). However, nonvaccine P p .229 P p .699 types were acquired faster ( ) and were carried for a shorter duration ( ) than were vaccine serotypes. P p .004 P ! .001 A previous episode of serotype 14 carriage was associated with delayed reacquisition of this serotype ( ) P p .005 and longer duration of carriage ( ). P 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.