Introduction: Expansion of immunisation programmes results in significant increases in vaccine costs. We present an analysis of the costs and outcomes of four different policy options relating to hepatitis B and Haemophilus influenzae type b. These were use of both vaccines (DPT-HepB-Hib), only one (DPT-HepB or DPT-Hib) or neither (DPT alone). Methods: Vaccine costs, treatment costs for hepatitis B and Haemophilus influenzae type b related illnesses, and the number of cases and deaths due to these illnesses were estimated for the expected birth cohort of 2007 in Uganda, for coverage with HepB and/or Hib vaccines of 0% and 80%. Costing is based on unit costs for vaccines and treatment of respective diseases due to each policy option, at 2003 constant prices discounted to 2007, and according to epidemiological estimates for each condition and sequelae. The cost-effectiveness of each policy option is determined for cost per child, cost per vaccine dose, cost per capita, per case, and death averted. Results: Considering vaccine and treatment costs combined, DPT-HepB is the cheapest option overall, followed by DPT-HepB-Hib, DPT, and DPT-Hib respectively. Cost per immunised child, including treatment costs would be USD $8.50 for a DPT-HepB option, increasing to USD $15.60, $20.80 and $30.30 for DPT-HepB-Hib, DPT, and DPT-Hib options respectively. A policy change from DPT to DPT-HepB or DPT-HepB-Hib would be associated with lower overall costs and fewer deaths. Sensitivity analysis corroborates these findings. A DPT-HepB-Hib option provides less cost per illness episode than DPT-HepB only if it costs under US $ 1.80. Conclusions: Using vaccine price alone to make policy decisions about vaccine options is misleading. Calculating treatment costs and expected health benefit provides more comprehensive information. At 2003 vaccine prices, DPT-HepB option is the cheapest option, with DPT-HepB and DPT-HepB-Hib more cost effective than DPT alone. DPT-HepB-Hib price under US$ 1.80 would make it the most cost-effective option available to countries
