Fitting a programmatic response to the hepatitis B virus epidemic in sub-Saharan Africa in the era of elimination

Chronic hepatitis B virus (HBV) infection is an important cause of liver cancer and cirrhosis and has a particularly high burden in sub-Saharan Africa, where access to treatment and prevention interventions against mother-to-child transmission remains limited. This thesis uses mathematical modelling to analyse the HBV epidemic and potential strategies for implementation of screening and treatment in a sub-Saharan African setting. Firstly, existing evidence on the HBV epidemic in sub-Saharan Africa is reviewed by both comparing different sets of modelled HBV prevalence estimates and conducting a scoping review of the published literature on HBV epidemiology and natural history. Data gaps on the chronic infection prevalence in children, burden of cirrhosis and contribution of mother-to-child transmission to new infections in the post-vaccination era are identified. Next, a dynamic model of HBV transmission is developed based on an existing framework and adapted to the sub-Saharan African context. Synthesising all available data from The Gambia in a Bayesian framework further reveals key uncertainties in natural history model parameters. Projections suggest that HBV elimination as a public health threat would be possible in The Gambia by 2030 with full scale-up of all available interventions, depending on the targets used to define it. Lastly, the model is used to investigate the population-level impact and cost-effectiveness of introducing screening and treatment in The Gambia, including different strategies for monitoring treatment-ineligible chronic carriers, targeting different segments of the population and repeated screening over time. The analysis shows that just a one-time population-based screening and treatment programme could substantially reduce HBV-related mortality in the Gambian population, and would be cost-effective if monitoring is reduced from the currently recommended annual frequency to every 5 years in under 45-year-olds. Overall, findings from this thesis provide guidance to policymakers on locally relevant strategies for implementation of treatment programmes in sub-Saharan Africa in the era of elimination, as well as an evidence base to inform further HBV modelling studies.