title: Nasopharyngeal colonization with heptavalent pneumococcal conjugate vaccine serotypes of Streptococcus pneumoniae with prolonged vaccine dosing intervals.
abstract: BACKGROUND
  Universal infant heptavalent pneumococcal conjugate vaccine (PCV-7) immunization, dosed near to the originally recommended schedule of a 3-dose series in the first 6 months of life, then a booster between 12 and 15 months, should reduce nasopharyngeal (NP) carriage of Streptococcus pneumoniae (Spn) PCV-7 types. The reduced availability of PCV-7 altered immunization schedules, particularly for third and fourth PCV-7 doses. We evaluated NP colonization in relation to originally recommended intervals and numbers of PCV-7 doses.
  
  
  METHODS
  Spn from NP cultures of a cohort of 106 normal children, obtained during 20 months of PCV-7 shortage, were identified and serotyped by standard methods.
  
  
  RESULTS
  Spn was detected in 153 of 418 cultures (37%). Age, >1 sibling, day-care attendance and prolonged PCV-7 dosing intervals were univariate risks for NP detection of PCV-7 types. PCV-7 strains comprised 7 of 15 (47%) of Spn before the first dose, 28 of 36 (78%) and 27 of 41 (66%), respectively, after the first and second dose and then 16 of 36 (44%) and 11 of 25 (44%) after the third and fourth doses. The risk of NP colonization with PCV-7 types was higher with intervals of >3 months between second and third doses and intervals of >8 months between the third and fourth doses. Multivariate analysis showed prolonged interval after the second and third PCV-7 doses and day-care attendance as risk factors for NP detection of PCV-7 strains.
  
  
  CONCLUSIONS
  Although PCV-7 serotypes were detected less after third and fourth PCV-7 doses, longer dosing intervals, particularly in day-care attendees, were associated with higher risk of PCV-7 detection in the NP.
authors.affiliation: Division of General Pediatrics, University of Louisville School of Medicine, 571 South Floyd Street, Louisville, KY 40202, USA. vfjone01@louisville.edu
authors.forename: Veronnie Faye
authors.initials: VF
authors.lastname: Jones
authors.forename: Christopher
authors.initials: C
authors.lastname: Harrison
authors.forename: Gordon G
authors.initials: GG
authors.lastname: Stout
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hopkins
mesh_terms: D002656:Child Day Care Centers; D015331:Cohort Studies; D004306:Dose-Response Relationship, Immunologic; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007115:Immunization Schedule; D007117:Immunization, Secondary; D007223:Infant; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D015999:Multivariate Analysis; D009305:Nasopharynx / Q000382:microbiology*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D012307:Risk Factors; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification*
chemical_list: D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines