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Polysaccharide vaccines for preventing serogroup A meningococcal meningitis
1National Centre for Epidemiology and Population Health, Australian National University, Canberra, ACT 0200, Australia. Mahomed.Patel@anu.edu.au
Insights
The serogroup A polysaccharide vaccine offers strong protection against meningococcal meningitis for the first year post-vaccination. Efficacy beyond the first year and in young children requires further investigation.
Area of Science:
- Immunology
- Vaccinology
- Epidemiology
Background:
- Polysaccharide serogroup A vaccine demonstrated efficacy in preventing meningococcal meningitis over two decades ago.
- Subsequent studies indicated potential age-specific variations in protection duration among young children.
Purpose of the Study:
- To evaluate the effectiveness of the polysaccharide serogroup A vaccine in preventing serogroup A meningococcal meningitis.
- To assess the duration of protection and the impact of booster doses in children under two years of age.
Main Methods:
- Systematic review of MEDLINE and Cochrane Controlled Trials Register.
- Inclusion of prospective controlled trials and non-experimental studies.
- Data synthesis using the Exact method for vaccine efficacy at 1, 2, and 3 years post-vaccination.
Main Results:
- Vaccine efficacy was 95% (95% CI 87%, 99%) within the first year across 8 trials.
- Protection extended into the second and third years, but without statistical significance.
- Limited statistical power in trials assessing booster doses for children under 18 months.
Conclusions:
- The vaccine provided strong protection for individuals over 5 years old in the first year post-vaccination.
- Protection beyond the first year was observed but not precisely quantifiable.
- Efficacy in children aged 1-5 years in developing countries was noted, with uncertainty for the youngest age groups.
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.
Objectives:
To determine the effect of polysaccharide serogroup A vaccine for preventing serogroup A meningococcal meningitis.
Search Strategy:
MEDLINE and the Cochrane Controlled Trials Register.
Selection Criteria:
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.
Data Collection And Analysis:
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.
Main 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.
Reviewer'S 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.