SUMMARYMeningococcal meningitis is a major public health problem in a large area of sub-Saharan Africa known as the meningitis belt. Disease incidence increases every dry season, before dying out with the first rains of the year. Large epidemics, which can kill tens of thousands of people, occur frequently but unpredictably every 6-14 years. It has been suggested that these patterns may be attributable to complex interactions between the bacteria, human hosts and the environment. We used deterministic compartmental models to investigate how well simple model structures with seasonal forcing were able to qualitatively capture these patterns of disease. We showed that the complex and irregular timing of epidemics could be caused by the interaction of temporary immunity conferred by carriage of the bacteria together with seasonal changes in the transmissibility of infection. This suggests that population immunity is an important factor to include in models attempting to predict meningitis epidemics.

Bexsero, a new vaccine against serogroup B meningococcal disease (MenB), was licensed in Europe in January 2013. In Germany, Bexsero is recommended for persons at increased risk of invasive meningococcal disease, but not for universal childhood vaccination. To support decision making we adapted the independently developed model for England to the German setting to predict the potential health impact and cost-effectiveness of universal vaccination with Bexsero(®) against MenB disease. We used both cohort and transmission dynamic mathematical models, the latter allowing for herd effects, to consider the impact of vaccination on individuals aged 0-99 years. Vaccination strategies included infant and adolescent vaccination, alone or in combination, and with one-off catch-up programmes. German specific data were used where possible from routine surveillance data and the literature. We assessed the impact of vaccination through cases averted and quality adjusted life years (QALY) gained and calculated costs per QALY gained. Assuming 65% vaccine uptake and 82% strain coverage, infant vaccination was estimated to prevent 15% (34) of MenB cases over the lifetime of one birth cohort. Including herd effects from vaccination increased the cases averted by infant vaccination to 22%, with an estimated 8461 infants requiring vaccination to prevent one case. In the short term the greatest health benefit is achieved through routine infant vaccination with large-scale catch-up, which could reduce cases by 24.9% after 5 years and 27.9% after 10 years. In the long term (20+ years) policies including routine adolescent vaccination are most favourable if herd effects are assumed. Under base case assumptions with a vaccine list price of €96.96 the incremental cost-effectiveness ratio (ICER) was >€500,000 per QALY for all considered strategies. Given the current very low incidence of MenB disease in Germany, universal vaccination with Bexsero(®) would prevent only a small absolute number of cases, at a high overall cost.

Efforts should focus on implementing multi-country, longitudinal seroprevalence and epidemiological studies, validating immune markers of protection, and improving surveillance, including more systematic molecular characterizations of the bacteria. Integrating climate and social factors into disease control strategies represents a high priority for optimizing the public health response and anticipating the geographic evolution of the African meningitis belt.