Targeting interventions to high-risk populations: Benefits and costs

Targeting prevention interventions to high-risk populations may increase intervention benefits, but identifying and/or finding the high-risk populations may increase intervention costs. We explore the costs and benefits of targeting in the context of human immunodeficiency virus (HIV) prevention in high-risk injection drug users (IDUs). Focusing interventions on such a population should maximize the number of HIV infections averted. Recruiting high-risk IDUs for such interventions, however, may be more difficult and costly. We base our analysis on an earlier model that determines the allocation of resources to two interventions, street outreach and methadone maintenance. The model seeks to minimize HIV incidence in a population of heterosexual IDUs and their non-injecting sex partners. We conclude that while targeting an inexpensive intervention like street outreach rarely proves to be cost-effective, even a costly targeting effort can increase cost effectiveness for an expensive, effective, narrowly focused intervention such as methadone maintenance.