Immunogenicity and safety of a meningococcal A conjugate vaccine in Africans

N Engl J Med. 2011 Jun 16;364(24):2293-304. doi: 10.1056/NEJMoa1003812.


Background: Group A meningococci are the source of major epidemics of meningitis in Africa. An affordable, highly immunogenic meningococcal A conjugate vaccine is needed.

Methods: We conducted two studies in Africa to evaluate a new MenA conjugate vaccine (PsA-TT). In study A, 601 children, 12 to 23 months of age, were randomly assigned to receive PsA-TT, a quadrivalent polysaccharide reference vaccine (PsACWY), or a control vaccine (Haemophilus influenzae type b conjugate vaccine [Hib-TT]). Ten months later, these children underwent another round of randomization within each group to receive a full dose of PsA-TT, a one-fifth dose of PsACWY, or a full dose of Hib-TT, with 589 of the original participants receiving a booster dose. In study B, 900 subjects between 2 and 29 years of age were randomly assigned to receive PsA-TT or PsACWY. Safety and reactogenicity were evaluated, and immunogenicity was assessed by measuring the activity of group A serum bactericidal antibody (SBA) with rabbit complement and performing an IgG group A-specific enzyme-linked immunosorbent assay.

Results: In study A, 96.0% of the subjects in the PsA-TT group and 63.7% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline; in study B, 78.2% of the subjects in the PsA-TT group and 46.2% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline. The geometric mean SBA titers in the PsA-TT groups in studies A and B were greater by factors of 16 and 3, respectively, than they were in the PsACWY groups (P<0.001). In study A, the PsA-TT group had higher antibody titers at week 40 than the PsACWY group and had obvious immunologic memory after receiving a polysaccharide booster vaccine. Safety profiles were similar across vaccine groups, although PsA-TT recipients were more likely than PsACWY recipients to have tenderness and induration at the vaccination site. Adverse events were consistent with age-specific morbidity in the study areas; no serious vaccine-related adverse events were reported.

Conclusions: The PsA-TT vaccine elicited a stronger response to group A antibody than the PsACWY vaccine. (Funded by the Meningitis Vaccine Project through a grant from the Bill and Melinda Gates Foundation; numbers, ISRCTN78147026 and ISRCTN87739946.).

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Africa
  • Antibodies, Bacterial / blood*
  • Double-Blind Method
  • Female
  • Haemophilus Vaccines
  • Humans
  • Immunologic Memory
  • Infant
  • Male
  • Meningococcal Vaccines / adverse effects
  • Meningococcal Vaccines / immunology*
  • Neisseria meningitidis / immunology*
  • Polysaccharides, Bacterial
  • Tetanus Toxoid
  • Vaccines, Conjugate / adverse effects
  • Vaccines, Conjugate / immunology


  • Antibodies, Bacterial
  • Haemophilus Vaccines
  • Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate
  • Meningococcal Vaccines
  • Polysaccharides, Bacterial
  • PsACWY vaccine
  • Tetanus Toxoid
  • Vaccines, Conjugate
  • meningococcal group A polysaccharide

Associated data

  • ISRCTN/ISRCTN78147026
  • ISRCTN/ISRCTN87739946