Hepatitis B virus (HBV) infection remains a global public health challenge that causes significant morbidity and mortality, (1) and the burden of disease is especially high in less-developed countries. (2) Since 2000, the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunisation) and the Vaccine Fund have accelerated the introduction of HBV vaccines in low-income countries by providing five years of funding for new and underused vaccines, including HBV vaccines. (3) As of April 2005, mainly as a result of these efforts, 158 of 192 WHO Member States had adopted routine infant or childhood vaccination against HBV (GAVI Working Group, unpublished data, 2005). Moreover, building on the success of phase 1 of the programme (2000-2005), more resources were mobilized, and the GAVI Alliance decided to extend its support for the 72 poorest countries for phase 2 (2006-2015). (4)
However, there is no guarantee of long-term support for HBV vaccines, and each recipient country is required to cofinance its immunization programme, gradually increasing its contribution to a self-sustainable level at the end of the current grant. (4) Therefore, despite the GAVI Alliance's extended support, each recipient country needs to be conscious of the financial sustainability of its HBV vaccination programme and, accordingly, each country will need information on the total amount of resources required to fund the programme. The introduction of other new and underused vaccines--for example, those against Haemophilus influenzae type b (Hib) and yellow fever--in an increasing number of countries may intensify competition for limited resources. Finally, there will inevitably be uncertainty surrounding the real-world benefits of vaccination (for example, the ability to achieve adequate vaccine coverage) and the resources required to implement and sustain programmes, (5) particularly in settings with weak health infrastructure, which will further complicate budget-related decisions.
In this context, decision-makers will likely benefit from additional information about whether an HBV vaccination programme is affordable and cost-effective. In addition, decision-makers will benefit from an explicit recognition that the information will be uncertain and from analyses that take into account this uncertainty. In part, this has been addressed by summarizing cost-effectiveness results using cost-effectiveness acceptability curves; these curves show the probability that a programme will be cost-effective as a function of different thresholds for acceptable cost-effectiveness ratios. (6) However, one limitation of this approach is that the total amount of resources required to fund a programme is not considered. (7) The cost-effectiveness affordability curve proposed by Sendi and Briggs overcomes this limitation because it presents the probabilities that a programme is simultaneously cost-effective and affordable as a function of both the threshold cost-effectiveness ratio and budgetary constraints. (8) To illustrate the usefulness of providing decision-makers with information on affordability and cost-effectiveness while formally accounting for uncertainty, we applied this approach to a real-world policy example: the programme to vaccinate infants against HBV in the Gambia.
Using the example, we first evaluated the programme's cost-effectiveness and derived cost-effectiveness acceptability curves. The cost-effectiveness of a programme was benchmarked in reference to specified thresholds, such as per-capita gross domestic product (GDP). A cost-effectiveness acceptability curve, constructed in the context of a multivariate uncertainty analysis, presents the probability that a programme will be cost-effective in relation to a range of different cost-effectiveness thresholds.
We next assessed affordability at country level in terms of the annual expected cost for the vaccination programme compared with a specified programme budget. …