Tigge Ensemble Weather Forecasts to Help Manage Meningitis in the Sahel

Meningitis epidemics in the Sahel have historically occurred with regularity, leading to the deaths of hundreds. Until 2010, the protection provided by the only available vaccine was so limited and short-lived that the only practical strategy for vaccination was reactive: waiting until an epidemic occurred in the region and then vaccinating in that region to prevent the epidemic's further growth. While a new vaccine has been developed that is effective and inexpensive enough to be used more broadly and proactively, it is only effective against serogroup A which causes the most common kind of bacterial meningitis in the Sahel. As a result, other strains have been occurring in the Sahel with limited vaccine that have been impacting thousands, potentially continuing the need for for reactive vaccination strategies as these new serogroups continue to circulate.

Because in the past, the reactive vaccine only provides protection for two to three years, does not prevent carriage, and does not induce herd immunity, retrospective analysis can estimate the impact of meningitis on a district with or without a reactive vaccination campaign and with or without advanced knowledge of weather conditions. This approach allows us to retrospectively assess how “perfect” weather information could have been used to allow public health officials to deploy vaccines sooner to areas in which the epidemics are likely to persist due to continued dryness and avoid vaccinating areas where the epidemics will end with higher humidity, mitigating the impact of the disease on human morbidity, mortality, and strained health-directed financial resources. However, in reality no forecast is perfect, and often ensemble approaches are the best option. In this context we investigated the application and skill of the Thorpex Tigge multi-center ensemble weather forecasts. In this talk we discuss our work to optimally blend the multi-model ensemble weather forecasts, and discuss the benefits of its application to more effectively allocate scare meningitis vaccine over single-model or climate forecasts. We also discuss ongoing efforts with the World Health Organization and ACMAD to test the utility of country-specific forecasts based on weather forecasts and current district-level disease incidence to help inform public health officials from several African countries during the vaccination decision-making process.