Meningococcal carriage by age in the African meningitis belt: a systematic review and meta-analysis

Abstract

Meningococcal carriage dynamics drive patterns of invasive disease. The distribution of carriage by age has been well described in Europe, but not in the African meningitis belt, a region characterised by frequent epidemics of meningitis. We aimed to estimate the age-specific prevalence of meningococcal carriage by season in the African meningitis belt. We searched PubMed, Web of Science, the Cochrane Library and grey literature for papers reporting carriage of Neisseria meningitidis in defined age groups in the African meningitis belt. We used a mixed-effects logistic regression to model meningococcal carriage prevalence as a function of age, adjusting for season, location and year. Carriage prevalence increased from low prevalence in infants (0.595% in the rainy season, 95% CI 0.482-0.852%) to a broad peak at age 10 (1.94%, 95% CI 1.87-2.47%), then decreased in adolescence. The odds of carriage were significantly increased during the dry season (OR 1.5 95% CI 1.4-1.7) and during outbreaks (OR 6.7 95% CI 1.6-29). Meningococcal carriage in the African meningitis belt peaks at a younger age compared to Europe. This is consistent with contact studies in Africa, which show that children 10-14 years have the highest frequency of contacts. Targeting older children in Africa for conjugate vaccination may be effective in reducing meningococcal transmission.

Keywords: Infectious disease epidemiology; meningitis-bacterial; meningococcal disease; meta-analysis; pharyngeal carriage.

Fig. 1.

Selection of studies on meningococcal carriage prevalence for systematic review and meta-analysis. For full details of all the papers that were reviewed, including reasons for exclusion, please contact the corresponding author.

Fig. 2.

Observed carriage prevalence measures and model predictions. Top panel: Circles show the data points included in the meta-analysis, with the larger circles representing a larger sample size. Solid line shows model predictions including random effects. Shaded ribbon shows 95% bias-corrected confidence intervals. Bottom panel: Circles show the data points included in the meta-analysis, with carriage prevalence adjusted for random effects intercept. Solid line shows model predictions excluding random effects. Shaded ribbon shows 95% bias-corrected confidence intervals. Dry season predictions are shown in red; rainy season in blue; outbreak in green.

Fig. 3.

Observed carriage prevalence and model predictions by leave-one-out cross-validation. (A) Distribution of model predictions for true zero observations. (B) True prevalence and prevalence predicted by leave-one-out cross-validation. Note the discontinuous scale to emphasise zero observations and the use of log scale for non-zero observations.