title: Polysaccharide vaccines for preventing serogroup A meningococcal meningitis.
abstract: BACKGROUND
  Controlled trials over two decades ago showed that the polysaccharide vaccine prevented serogroup A meningococcal meningitis. Subsequent non-experimental studies suggested age-specific variations in the duration of protection among young children.
  
  
  OBJECTIVE
  To determine the effect of polysaccharide serogroup A vaccine for preventing serogroup A meningococcal meningitis.
  
  
  METHODS
  MEDLINE and the Cochrane Controlled Trials Register.
  
  
  METHODS
  The first stage of the review included prospective controlled trials. The second stage included non-experimental studies that addressed questions unanswered by the trials, i.e. the duration of protection and the effect of a booster dose in children under 2 years of age.
  
  
  METHODS
  One reviewer assessed the methodological quality of the trials, and two reviewers independently identified and assessed the non-experimental studies. Data from the trials were pooled using the Exact method to assess vaccine efficacy at 1, 2 and 3 years post- vaccination.
  
  
  RESULTS
  The protective effect within the first year was consistent across all 8 trials, vaccine efficacy was 95% (Exact 95% CI 87%, 99%). Protection extended into the second and third year after vaccination, but the results did not attain statistical significance. The only trial that assessed the effect of a booster dose in children less than 18 months old, lacked adequate statistical power. In the three other trials that included children less than 6 years old (one in Sudan and two in Nigeria), none of the vaccinated children developed meningitis, but the results did not attain statistical significance. Data from the two non-experimental studies included in this review were not pooled with the trial data because of methodological limitations.
  
  
  CONCLUSIONS
  For the first year after vaccination, the vaccine was strongly protective in participants over 5 years of age. It was also protective beyond the first year after vaccination, but the level of vaccine efficacy could not be determined with precision. Children aged 1 to 5 years in developing countries were protected, but the level of efficacy among the youngest children could not be determined. While the vaccine was strongly protective among children aged 3 months and over in developed countries, the number of participants aged under 2 years was too small to draw firm conclusions on the protective effect of, or need for, a booster dose of vaccine.
authors.affiliation: National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT 0200, Australia. Mahomed.Patel@anu.edu.au
authors.forename: M
authors.initials: M
authors.lastname: Patel
authors.forename: C K
authors.initials: CK
authors.lastname: Lee
mesh_terms: D006801:Humans; D008585:Meningitis, Meningococcal / Q000276:immunology / Q000517:prevention & control*; D009345:Neisseria meningitidis / Q000145:classification / Q000276:immunology; D011134:Polysaccharides; D011446:Prospective Studies; D018074:Vaccines, Conjugate / Q000627:therapeutic use*
chemical_list: D011134:Polysaccharides; D018074:Vaccines, Conjugate