title: Influence of Age on Antibody Response and Persistence Following Immunization With MenAfriVac.
abstract: BACKGROUND
  A meningococcal group A conjugate vaccine, PsA-TT (MenAfriVac), developed through the Meningitis Vaccine Project and manufactured by the Serum Institute of India, Ltd, was tested in multiple clinical trials conducted mainly in Africa. The impact of age at which subjects were vaccinated on immune response and persistence postimmunization with PsA-TT was the main focus of the current analysis.
  
  
  METHODS
  Subjects who were vaccinated with a single dose of 10 µg of PsA-TT at 12-23 months or 22-33 months of age in study A conducted in Mali and The Gambia; at 2-10 years, 11-17 years, or 18-29 years of age in study B conducted in Mali, The Gambia, and Senegal; and at 14-18 weeks, 9-12 months, or 12-18 months of age in study C conducted in Ghana are included in the current analysis. Immunogenicity was measured by group A serum bactericidal antibody (SBA) titer with baby rabbit complement.
  
  
  RESULTS
  Significant differences in SBA titers were found among the age groups in studies B and C both 28 days and 1 year postimmunization. A significant difference in SBA titers between age groups 12-23 months and 22-33 months was only observed 1 year postimmunization in study A. Antibody titers remained at similar levels from 1 to 2 years postimmunization for subjects vaccinated at 12-23 months in study A and at 9-12 months or 12-18 months of age in study C.
  
  
  CONCLUSIONS
  Subjects immunized at different ages had different postimmunization immune responses as measured by SBA titers. Toddlers tended to have higher immune responses than infants. This pattern persisted at least 1 year postimmunization.
  
  
  BACKGROUND
  ISRCTN78147026 (study A), ISRCTN87739946 (study B), and ISRCTN82484612 (study C).
authors.affiliation: Meningitis Vaccine Project, PATH, Seattle, Washington.
authors.forename: Yuxiao
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Plikaytis
authors.affiliation: Meningitis Vaccine Project, PATH, Ferney-Voltaire, France Meningitis Vaccine Project, Department of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Preziosi
authors.affiliation: Vaccine Evaluation Unit, Public Health England, Royal Manchester Infirmary, United Kingdom.
authors.forename: Ray
authors.initials: R
authors.lastname: Borrow
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa; D000367:Age Factors; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D000917:Antibody Formation; D001770:Blood Bactericidal Activity; D002648:Child; D002675:Child, Preschool; D003165:Complement System Proteins; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D022401:Meningococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D011817:Rabbits; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; C573970:MenAfriVac; D022401:Meningococcal Vaccines; D003165:Complement System Proteins
keywords: MenAfriVac; age; meningococcal group A conjugate vaccine; serum bactericidal antibody