title: Predictors of pneumococcal conjugate vaccine immunogenicity among infants and toddlers in an American Indian PnCRM7 efficacy trial.
abstract: BACKGROUND
  Pneumococcal conjugate vaccines are important for the prevention of serious illness and death among infants. Factors associated with pneumococcal conjugate vaccine immunogenicity have not been explored.
  
  
  METHODS
  Children <24 months of age received 2, 3, or 4 doses of 7-valent pneumococcal conjugate vaccine (PnCRM7) or control vaccine depending on age at enrollment. Serum samples were tested for serotype-specific antibodies by enzyme-linked immunosorbant assay. Multiple linear regression was used to determine predictors of immunogenicity.
  
  
  RESULTS
  Among 315 PnCRM7-vaccinated subjects and 295 control subjects enrolled at <7 months of age, geometric mean concentrations (GMCs) of antibodies were significantly higher after dose 3 than after dose 2 for all serotypes except type 4. The proportion of subjects with antibody concentrations > or =5.0 micro g/mL was higher for all serotypes, but the proportion with concentrations > or =0.35 micro g/mL was higher only for types 6B and 23F. Three-dose and 2-dose regimens for those 7-11 and 12-23 months of age, respectively, were highly immunogenic. Increased maternal antibody concentrations were associated with reduced responses to dose 1 and 3 but not to dose 4 of PnCRM7.
  
  
  CONCLUSIONS
  Maternal antibody is associated with a reduced infant response to PnCRM7 but does not interfere with immune memory. In infants, a third priming dose increases the antibody GMC and the proportion achieving an antibody concentration > or =5.0 micro g/mL but has little impact on the proportion achieving a concentration > or =0.35 micro g/mL.
authors.affiliation: Center for American Indian Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. klobrien@jhsph.edu
authors.forename: Katherine L
authors.initials: KL
authors.lastname: O'Brien
authors.forename: Jennifer
authors.initials: J
authors.lastname: Moisi
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Moulton
authors.forename: Dace
authors.initials: D
authors.lastname: Madore
authors.forename: Angelia
authors.initials: A
authors.lastname: Eick
authors.forename: Ray
authors.initials: R
authors.lastname: Reid
authors.forename: Robert
authors.initials: R
authors.lastname: Weatherholtz
authors.forename: Eugene
authors.initials: E
authors.lastname: Millar
authors.forename: Diana
authors.initials: D
authors.lastname: Hu
authors.forename: Jill
authors.initials: J
authors.lastname: Hackell
authors.forename: Robert
authors.initials: R
authors.lastname: Kohberger
authors.forename: George
authors.initials: G
authors.lastname: Siber
authors.forename: Mathuram
authors.initials: M
authors.lastname: Santosham
mesh_terms: D000367:Age Factors; D000907:Antibodies, Bacterial / Q000097:blood*; D001942:Breast Feeding; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007115:Immunization Schedule; D007117:Immunization, Secondary; D007198:Indians, North American; D007223:Infant; D016014:Linear Models; D008297:Male; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D011008:Pneumococcal Infections / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology; D014481:United States
chemical_list: D000907:Antibodies, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines