MODELING THE IMPACT AND COST-EFFECTIVENESS OF HIV PREVENTION EFFORTS

Objectives: This study explores how mathematical models can be used to examine the relationship between the effectiveness and costs of diffe rent prevention strategies. The analysis, based on a model designed to simulate the spread of HIV in sub-Saharan Africa, illustrates how the impact and relative cost-effectiveness of a prevention programme are sensitive to a number of factors including the rate of spread of HIV p rior to the introduction of the programme, the measure used to evaluat e the impact of the programme, and the point when the programme is int roduced in the epidemic. Results: Assessing the impact and cost-effect iveness of different HIV prevention strategies is problematic. Not onl y are there difficulties in collecting the relevant data, but the impa ct of a prevention programme may be highly non-linear in character bec ause of the many factors that determine the net rate of viral transmis sion. The long incubation period of HIV further complicates the analys is as the benefits from preventing a case of infection extend over a n umber of years. Conclusions: The results highlight the need to collect more data on the impact and costs of prevention programmes if we are to ensure that the available resources for HIV prevention are to be us ed both efficiently and equitably.