Economic evaluation of vaccination programs: Cost-effectiveness, externalities, and affordability of hepatitis B vaccination

Vaccination is considered one of the most cost-effective public health interventions. Although hepatitis B virus (HBV) infection, which causes significant morbidity and mortality from cirrhosis and primary liver cancer, is preventable using safe and effective vaccines, social and economic barriers hamper the global control of HBV infection, and hepatitis B remains a global health challenge. Also, because the burden and epidemiological features of the disease are disproportionately distributed, each country faces different policy questions in controlling HBV using vaccines. In industrialized countries, program efficiency and political commitments are of primary concern, while in low-income countries, financial sustainability must also be taken into consideration.; This dissertation seeks to develop and apply various types of mathematical models to evaluate the cost-effectiveness, externalities, and affordability of different hepatitis B vaccination programs in two different settings: the U.S., a representative of low-endemic industrialized countries, and The Gambia, a representative of high-endemic lowest-income countries.; Chapter 1 evaluates the cost-effectiveness of hepatitis B vaccination strategies targeting potentially high-risk persons attending publicly funded HIV counseling and testing sites (CTSs) in the U.S. The results show that routine vaccination would be both more effective and cost-effective than screening strategies. The findings also imply that integrating a routine hepatitis B prevention service into existing HIV CTSs would be a highly cost-effective public health intervention and may also have positive effects on the control of other types of viral diseases.; Chapter 2 seeks (1) to develop a mathematical model that can describe the transmission dynamics of HBV and calitrate the model, (2) to evaluate the overall impact of a future vaccination policy identified as cost-effective in Chapter 1 on the control of HBV at the national level over time, and (3) to quantify positive externalities due to the vaccination policy. The study shows that a catch-up vaccination targeting high-risk adults would significantly reduce HBV incidence among those adults, accelerating the control of HBV in the U.S. The study also finds that vaccinating high-risk individuals would provide positive externalities to society, lowering HBV incidence even among unvaccinated low-risk individuals. About 30% of the cumulative number of HBV infections prevented due to the selective vaccination are estimated to come from externalities, and the externalities increase with vaccine coverage in a non-linear pattern.; Chapter 3 assesses the cost-effectiveness and affordability of routine infant hepatitis B vaccination in The Gambia. Although The Gambia is receiving support for the vaccination program from the Global Alliance on Vaccines and Immunization, financial sustainability after the 5-year grant remains a big challenge to maintaining the program. The findings show that universal infant hepatitis B vaccination is highly cost-effective and has the potential to be affordable even with relatively low budgets in The Gambia. However, for the program to be affordable, the problem of narrowing the current funding gap awaits solution, and a full analysis of affordability requires further research.