Neisseria meningitidis carriage by age: a systematic review

Objectives: Whilst the introduction of meningococcal serogroup C vaccine in 1999 has successfully reduced the number of cases of disease caused by this serogroup, meningococcal disease remains an important public health problem in the UK. Most cases of meningococcal disease in the UK are now caused by serogroup B and a number of promising vaccine candidates are in clinical trial. Infectious disease models can be used as tools to help identify the optimal introduction strategy for new vaccines. Due to the epidemiology of meningococcal meningitis, such models must take account of the transmission dynamics of the organism and require information on carriage by age. However, few recent large-scale carriage studies in all age groups have been undertaken in the UK due to logistic and cost reasons. The purpose of this systematic review was to obtain more robust estimates of carriage by age, which could be used within a transmission dynamic model of meningococcal disease. Methods: The databases EMBASE, Medline, Web of Science and the Cochrane Library were searched for papers reporting carriage of Neisseria meningitidis in defined age groups. Papers published after 1969 reporting on at least 100 individuals sampled/swabbed for meningococcal carriage in any language were included. Papers reporting studies from Africa, Asia and Russia , China and Japan were excluded due to thebecause the epidemiology of meningococcal disease is different epidemiology of meningococcal infection in these countries compared to the UK (e.g. i.e. predominance of large proportion of group A disease). Studies in among close contacts of a cases or in military personnel (with the exception of those sampled on day of entry) were also excluded. References of relevant and review papers were checked for additional studies. Results: After removing duplicates the search returned 1464 papers; after reviewing titles and abstracts, the full text was obtained for 242 papers. At the time of writing a number of foreign text papers were still being processed; the preliminary results presented here are for papers in English (n=177) identified in the initial search. Full results, including point estimates of carriage by age will be available for conference. [Will need to be changed] 40 papers satisfied the inclusion criteria reporting studies from 18 countries: Australia (1), Belgium (1), Canada (2), the Czech Republic (1), Denmark (2), Germany (1), Greece (4), Israel (1), Lebanon (1), the Netherlands (2), Norway (3), Poland (1), Saudi Arabia (1), Spain (3), Thailand (1), Turkey (1), the UK (12) and USA (2). There were 5 longitudinal studies and 29 papers providing carriage prevalence for more than one age or age range. Whilst there are large differences in carriage by age reported by individual studies, a general trend of low carriage prevalence in young children and older adults and increased carriage in teenagers and young adults can be seen (figure 1). Conclusion: Robust estimates of carriage prevalence by age are required to parameterise transmission dynamic models of meningococcal meningitis, which can inform vaccination schedule development. In the absence of a recent large-scale carriage study across all age groups in the UK, this systematic review provides estimates of carriage by age, which can be used for infectious disease modelling.