Economic rate of discount and estimating cost benefit of viral immunisation programmes

Many individual and societal decisions over purchase (or investment) involv e consideration of timing, in that either the price may be paid now and the benefit enjoyed some time in the future or the converse the benefit enjoye d now and the price paid later. Since most individuals generally prefer the present to the future, economic theory has conventionally discounted futur e costs or benefits to estimate 'net present values'. The rationale for thi s is principally based on future uncertainty. In recent years, economists h ave turned their attention to valuing health as an economic 'good'. Observa tions of individual behaviour would imply that individuals discount future health, as other potential benefits, mostly because there is some uncertain ty about their futures. Although economic theory is strongly predicated on the 'sovereignty of the individual', it does not necessarily follow that so ciety discounts the future as do individuals, since for society the future is not so uncertain. Society's endorsement of many public health and preventive medicine objecti ves, which seek health gains in the future (rather than the present), imply that society's rate of discount may be appreciably lower than that of indi viduals. In immunisation, arguably one of the most effective of preventive measures, there is the additional benefit to others attributable to herd im munity. This paper argues that the future health gains for society arising from immunisation should not be underestimated by application of inappropri ate discounting. Copyright (C) 1999 John Wiley & Sons, Ltd.