Cost-effectiveness of Haemophilus influenza type b vaccine in low and middle income countries

Presenter: Ulla Kou Griffiths, London School of Hygiene & Tropical Medicine

Abstract

Rationale: Haemophilus influenza type b (Hib) vaccine became available during the late 1980s and was rapidly introduced into routine childhood vaccination programmes in high income countries. Numerous subsequent studies have illustrated a near elimination of invasive Hib disease in young children in these settings. Since the year 2000, the GAVI Alliance has offered support for Hib vaccine to the 75 poorest countries of the world, but uptake of the vaccine through this mechanism has only seriously advanced during the last few years. Several middle income countries have not yet decided to include the vaccine into their routine immunization programs. Since Hib disease is difficult to detect, the impact of the vaccine can only be demonstrated in settings with relatively sophisticated surveillance systems in place. To assist countries in making decisions about Hib vaccine introduction, and in the absence of clinical data, mathematical models can provide a useful framework for estimating the projected impact and cost-effectiveness of vaccination.

Objectives: To demonstrate the cost-effectiveness of Hib vaccine in low and middle income countries according to geography and income group.

Methodology: A static cohort model was used to estimate Hib vaccine impact. Person-years lived between 1 and 59 months of age were based on UN projections of annual live births and rates of childhood mortality. Hib disease was divided into three syndromes: 1) Hib meningitis, 2) Hib pneumonia and 3) Hib non-pneumonia non-meningitis (NPNM). Country-specific estimates of incidence and case fatality ratios for the three syndromes were provided by the WHO Global Burden of Hib Disease Project. The proportion of surviving Hib meningitis patients suffering from different types of lifelong disability, such as deafness, motor abnormalities and mental retardation, was based on a recent systematic literature review.
Hib disease treatment costs were divided into patient -specific costs and costs per hospital bed day and outpatient visit. The lengths of stay in hospital due to meningitis and pneumonia were estimated from a number of country-specific studies. Country specific unit cost values were used when available.
Since UNICEF is the procurement agency for GAVI supported countries, the price of Hib vaccine is readily available for these settings. For middle income countries, the Hib vaccine price was collected from a selection of countries and extrapolations were made to settings with no public information on this and to countries not yet procuring the vaccine.
Extensive probabilistic uncertainty and scenario analyses were undertaken to estimate plausible ranges for the disease impact and cost-effectiveness results.

Results: When using the WHO cost-effectiveness threshold, Hib vaccine can be considered cost-effective, as the costs per DALY averted are less than GDP per capita in both low and middle income countries settings. The analysis illustrates that for high mortality countries, Hib vaccine prevents approximately 4% of the current under-five childhood mortality.

Conclusion: Our analysis illustrates that Hib vaccination is an important tool for the prevention of under five mortality. According to WHO thresholds, the vaccine can be considered a cost-effective intervention in low and middle income countries.