Streptococcus pneumoniae serotypes isolated from the middle ear fluid of Costa Rican children following introduction of the heptavalent pneumococcal conjugate vaccine into a limited population

► Middle ear fluid S. pneumoniae strains from Costa Rican children between 1999 and 2008. ► Access to PCV-7, outside the NIP, was limited in Costa Rica from 2004 and used in <5% of birth cohort. ► Middle ear fluid isolates collected between 1999 and 2003 and between 2004 and 2008 were compared. ► Changes in serotype distribution and antimicrobial susceptibility were observed. ► Between 2004 and 2008, PCV-13 offered the highest potential vaccine coverage.