Meningococcal carriage by age: a systematic review and meta-analysis

Background Neisseria meningitidis is an important cause of meningitis and septicaemia, but most infected individuals experience a period of asymptomatic carriage rather than disease. Previous studies have shown that carriage rates vary by age and setting; however, few have assessed carriage across all ages. We aimed to estimate the age-specific prevalence of meningococcal carriage. Methods We searched Embase, Medline, Web of Science, the Cochrane Library, and grey literature for papers reporting carriage of N meningitidis in defined age groups in European countries or in countries with a similar epidemiological pattern (where disease caused by serogroups B and C predominates). We used mixed-effects logistic regression with a natural cubic spline to model carriage prevalence as a function of age for studies that were cross-sectional or serial cross-sectional. The model assessed population type, type of swab used, when swabs were plated, use of preheated plates, and time period (decade of study) as fixed effects, with country and study as nested random effects (random intercept). Findings Carriage prevalence increased through childhood from 4.5% in infants to a peak of 23.7% in 19-year olds and subsequently decreased in adulthood to 7.8% in 50-year olds. The odds of testing positive for carriage decreased if swabs were not plated immediately after being taken compared with if swabs were plated immediately (odds ratio 0.46, 95% CI 0.31-0.68; p=0.0001). Interpretation This study provides estimates of carriage prevalence across all ages, which is important for understanding the epidemiology and transmission dynamics of meningococcal infection.