THE BURDEN OF HAEMOPHILUS-INFLUENZAE TYPE-B DISEASE IN AUSTRALIA AND AN ECONOMIC APPRAISAL OF THE VACCINE PRP-OMP

Objectives: To estimate the incidence and sequelae of Haemophilus influenzae type b disease (Hib) in the Australian population, and to evaluate the costs and outcomes of a vaccination program using the vaccine PRP-OMP at two, four and 12 months. Design: The evaluation was based on a decision analytic model developed by Merck Sharp and Dohme (Australia) Pty Ltd, to predict the number of children who would contract Hib, and suffer mild or severe sequelae or die as a result. The state of health of a cohort of children was modelled each month over a five-year period. A survey of medical records and interviews with parents of children who contracted meningitis in Western Australia from 1984-1990 was undertaken to provide data on the extent and costs of sequelae. Results: The incidence of Hib among non-Aboriginal Australians under five years of age was estimated as 53 per 100 000, and 460 per 100 000 among Aborigines. In a single year at least 630 children may contract Hib, up to 19 may die, and a further 46 may have neurological damage, this being severe in up to 18 children. The number of deaths could be reduced by 17 per year and a further 25 cases of severe and 16 cases of mild disability could be averted. At a price of $20 per dose, and a 5% discount rate, the expected cost per year of life extended by a vaccination program is $3148. When adjusted for the increased number of years without neurological impairment, the incremental cost per quality adjusted life year (QALY) is $1965. Compared with a single vaccine at 18 months, the incremental cost per additional QALY gained is $5047. A separate analysis of the Aboriginal population showed that the proposed vaccination program would be of significant benefit, leading to a saving of resources.