title: Immunogenicity of an investigational quadrivalent Neisseria meningitidis-diphtheria toxoid conjugate vaccine in 2-year old children.
abstract: BACKGROUND
  One dose of a quadrivalent meningococcal conjugate (MC-4) vaccine elicits higher group C bactericidal responses in 2-year olds than a U.S.-licensed quadrivalent polysaccharide (MPS-4) vaccine [Granoff DM, Harris SL. Protective activity of group C anticapsular antibodies elicited in 2-year olds by an investigational quadrivalent Neisseria meningitidis-diptheria toxoid conjugate vaccine. Pediatr Infect Dis J, 2004;23:490-7].
  
  
  OBJECTIVE
  Assess immunogenicity and persistence of serum antibody to capsular groups A, Y and W-135 in 2-year old children immunized with MC-4 vaccine.
  
  
  METHODS
  Measurement of antibody responses in sera from a multicenter randomized trial comparing MC-4 and MPS-4 vaccines.
  
  
  RESULTS
  At 1 month, the group A serum bactericidal GMT was higher in the MC-4 than the MPS-4 group (P < 0.001) but there were no significant differences at 6 months. At 6 months, the respective Y and W-135 GMTs were higher in the MC-4 group (P < 0.05) but there were no differences at 1 month. The higher W-135 bactericidal titers reflected higher antibody avidity in the MC-4 group (P < 0.0001) and avidity maturation between 1 and 6 months (P < 0.05). At 2-year post-vaccination, the proportion of MC-4 immunized children with bactericidal titers > or =1:4 (presumed to be protective) was 15.0% (group A), 32.5% (group Y) and 45% (group W-135), as compared with 2.5, 15.4 and 17.5%, respectively, in unvaccinated children (P < 0.01 for group W-135; P < 0.05 for group A, and P = 0.07 for Y).
  
  
  CONCLUSIONS
  One dose of the MC-4 vaccine in 2-year olds elicits higher A, Y and W-135 bactericidal titers than MPS-4 vaccine. Compared with unvaccinated children, serum antibody titers remain elevated for 2 years after MC-4 vaccination. However, many vaccinated children have titers <1:4 and may require a booster dose for sustained protection.
authors.affiliation: Children's Hospital Oakland Research Institute, CA 94609, USA. drgranoff@chori.org
authors.forename: Dan M
authors.initials: DM
authors.lastname: Granoff
authors.forename: Amy
authors.initials: A
authors.lastname: Morgan
authors.forename: Jo Anne
authors.initials: JA
authors.lastname: Welsch
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D001770:Blood Bactericidal Activity; D002648:Child; D002675:Child, Preschool; D004168:Diphtheria Toxoid / Q000276:immunology*; D006801:Humans; D022401:Meningococcal Vaccines / Q000276:immunology*; D013997:Time Factors; D018074:Vaccines, Conjugate / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D004168:Diphtheria Toxoid; D022401:Meningococcal Vaccines; D018074:Vaccines, Conjugate