title: Hyporesponsiveness to re-challenge dose following pneumococcal polysaccharide vaccine at 12 months of age, a randomized controlled trial.
abstract: BACKGROUND
  To evaluate the immunological impact of the 23-valent pneumococcal polysaccharide vaccine (23vPPS) at 12 months, for children who have received zero to three infant doses of seven-valent pneumococcal conjugate vaccine (PCV), on responses to a subsequent exposure to a small dose of 23vPPS (mPPS).
  
  
  METHODS
  Five hundred and fifty-two Fijian infants were stratified by ethnicity and randomized into eight groups to receive zero, one, two, or three PCV doses at 14 weeks, six and 14 weeks, or six, ten, and 14 weeks. Within each group, half received 23vPPS at 12 months and all received mPPS at 17 months. Sera were taken prior and one month post-mPPS.
  
  
  RESULTS
  By 17 months, geometric mean antibody concentrations (GMC) to all 23 serotypes in 23vPPS were significantly higher in children who had received 23vPPS at 12 months compared to those who had not. Post-mPPS, children who had not received the 12 month 23vPPS had a significantly higher GMC for all PCV serotypes compared with those who had (each p<0.02). For the non-PCV serotypes, children who had not received the 12 month 23vPPS had significantly higher GMC for six of 16 non-PCV serotypes (7F, 9N, 12F, 19A, 22F, 33F) than those who did (each p<0.02). After adjusting for the pre-mPPS level, exposure to 23vPPS was associated with a lower response to mPPS for all serotypes (each p<0.001).
  
  
  CONCLUSIONS
  Despite higher antibody concentrations at 17 months in children who had received 23vPPS at 12 months, the response to a re-challenge was poor for all 23 serotypes compared to children who had not received the 12 month 23vPPS.
authors.affiliation: Centre for International Child Health, Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Victoria, Australia. fmruss@unimelb.edu.au
authors.forename: F M
authors.initials: FM
authors.lastname: Russell
authors.forename: J R
authors.initials: JR
authors.lastname: Carapetis
authors.forename: A
authors.initials: A
authors.lastname: Balloch
authors.forename: P V
authors.initials: PV
authors.lastname: Licciardi
authors.forename: A W J
authors.initials: AW
authors.lastname: Jenney
authors.forename: L
authors.initials: L
authors.lastname: Tikoduadua
authors.forename: L
authors.initials: L
authors.lastname: Waqatakirewa
authors.forename: J
authors.initials: J
authors.lastname: Pryor
authors.forename: J
authors.initials: J
authors.lastname: Nelson
authors.forename: G B
authors.initials: GB
authors.lastname: Byrnes
authors.forename: Y B
authors.initials: YB
authors.lastname: Cheung
authors.forename: M L K
authors.initials: ML
authors.lastname: Tang
authors.forename: E K
authors.initials: EK
authors.lastname: Mulholland
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D005260:Female; D005367:Fiji; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods*; D007223:Infant; D008297:Male; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: C414006:23-valent pneumococcal capsular polysaccharide vaccine; D000907:Antibodies, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines