title: Serotype-specific avidity is achieved following a single dose of the 7-valent pneumococcal conjugate vaccine, and is enhanced by 23-valent pneumococcal polysaccharide booster at 12 months.
abstract: OBJECTIVE
  To evaluate whether the avidity of serotype-specific IgG to pneumococcal serotypes is enhanced by an increased number of doses of the 7-valent pneumococcal conjugate vaccine (PCV) in infancy or by a 12 month 23-valent pneumococcal polysaccharide vaccine (23vPPS) booster, and/or subsequent re-exposure to a small dose of pneumococcal polysaccharide antigens (mPPS) at 17 months.
  
  
  METHODS
  Fijian infants aged 6 weeks were recruited, stratified by ethnicity and randomized to 8 groups to receive 0, 1, 2, or 3 doses of PCV, with or without 23vPPS at 12 months. All children received mPPS at 17 months of age. Avidity of serotype-specific IgG for PCV serotypes in the first 12 months and for all 23vPPS serotypes thereafter was assessed by EIA after sodium thiocyanate elution.
  
  
  RESULTS
  At one month post primary series, the 2 and 3 PCV dose groups demonstrated similar avidity, with the single dose group tending to have lower avidity. However, by age 9 months, the single dose group had similar avidity to the 2 and 3 PCV groups for most serotypes. The 23vPPS booster enhanced affinity maturation for most serotypes and this was most marked in those groups that received a single PCV dose. There was little further increase following the mPPS.
  
  
  CONCLUSIONS
  By 9 months of age, similar avidity can be induced following one, 2 or 3 doses of PCV. A 23vPPS booster at 12 months enhanced affinity maturation with an increase in antibody avidity for most serotypes. Subsequent re-challenge with mPPS at 17 months did not further enhance the avidity of serotype-specific response in the 12 month 23vPPS groups.
authors.affiliation: Centre for International Child Health, Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia. fmruss@unimelb.edu.au
authors.forename: F M
authors.initials: FM
authors.lastname: Russell
authors.forename: A
authors.initials: A
authors.lastname: Balloch
authors.forename: P V
authors.initials: PV
authors.lastname: Licciardi
authors.forename: J R
authors.initials: JR
authors.lastname: Carapetis
authors.forename: L
authors.initials: L
authors.lastname: Tikoduadua
authors.forename: L
authors.initials: L
authors.lastname: Waqatakirewa
authors.forename: Y B
authors.initials: YB
authors.lastname: Cheung
authors.forename: E K
authors.initials: EK
authors.lastname: Mulholland
authors.forename: M L K
authors.initials: ML
authors.lastname: Tang
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology*; D000915:Antibody Affinity / Q000187:drug effects / Q000276:immunology*; D000918:Antibody Specificity; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007117:Immunization, Secondary; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007223:Infant; D007700:Kinetics; D011008:Pneumococcal Infections / Q000276:immunology* / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology; D012703:Serotyping; D016037:Single-Blind Method; D013296:Streptococcus pneumoniae / Q000145:classification / Q000276:immunology*; D016896:Treatment Outcome; D014611:Vaccination
chemical_list: C414006:23-valent pneumococcal capsular polysaccharide vaccine; D000907:Antibodies, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines