This paper identifies an important paradigm shift in social research on HIV transmission, drug abuse, and risk reduction research. The article describes the key research trends and the institutional support for social network analysis in the HIV and drug risk field for the past decade. Key hypotheses and recommended areas for future research are identified.

ed by behavioural reversals. 5) Targeting can be the most effective vaccine strategy per vaccinated individual, but may not be the most effective use of a vaccine. Targeting is less likely to be appropriate for a 'leaky' vaccine where the number of challenges influence the chances of a breakthrough infection. Introduction Historically vaccines have been introduced assuming that they are highly efficacious. However, as the immunological challenges of vaccine development increase then it is likely that the efficacy of vaccine products will decline. It is conceivable that the first generation of HIV vaccines with an efficacy demonstrable in vaccine trials will not have extremely high efficacy. The acceptability of low efficacy vaccines will depend upon three main factors: their cost; the willingness of individuals to accept a less efficacious product; and the epidemiological effectiveness expected and demanded by decision makers if a vaccine is to be used. The work presented here uses a