AN ECONOMIC-ANALYSIS OF ALTERNATIVES FOR CHILDHOOD IMMUNIZATION AGAINST HAEMOPHILUS-INFLUENZAE TYPE-B DISEASE

Cost-effectiveness and cost-utility analyses of immunisation strategie s against invasive Haemophilus influenzae type b (Hib) disease in Aust ralia were based on a hypothetical birth cohort of 250000 non-Aborigin al Australian children. The model predicted that, without immunisation , 625 cases of invasive Hib disease would occur in under-five-year-old s, with direct costs of $10.2 million. Universal public sector vaccina tion beginning before six months of age (6MVAC) prevented 80 per cent of cases; vaccination at 12 months (12MVAC) 62 per cent and at 18 mont hs (18MVAC) 46 per cent. At a vaccine cost of $15 per dose, 18MVAC gav e the lowest cost per quality-adjusted life year (QALY) over a wide ra nge of model assumptions, with 6MVAC the 'best' alternative. The best estimate ($ per QALY) for 6MVAC was $6930 (three doses), for 12MVAC $9 136 (two doses) and for 18MVAC $1231 (one dose). The cost per QALY of single dose catch-up immunisation of older children was estimated at $ 8630 at two years, $27000 at three years and $117000 at four years if done at a scheduled visit; these values were increased if an additiona l medical visit was included. The threshold cost per vaccine dose at w hich an immunisation program became cost-saving was estimated for 6MVA C, 12MVAC and 18MVAC as $11, $10 and $14. Even under a worst-case scen ario, an immunisation program at 6, 12 or 18 months became cost-saving if indirect costs of death were included. Comparison with previous an alyses revealed the importance of the incidence and age distribution o f disability and assumptions about vaccine administration costs in det ermining model outcomes.