Defining high HIV incidence subgroups of Australian homosexual men: implications for conducting HIV prevention trials in low HIV prevalence settings.

OBJECTIVES: The aim of the study was to assess whether subpopulations with sufficiently high HIV incidences for HIV prevention trials can be identified in low HIV incidence settings such as Australia.
METHODS: In a community-based cohort study of HIV-negative homosexually active men in Sydney, Australia, potential risk factors associated with an annual HIV incidence of ≥2 per 100 person-years (PY) were identified. A stepwise procedure ranked these factors according to HIV incidence, to create a 'high-incidence' subgroup of participants. Willingness to participate in HIV prevention trials was assessed.
RESULTS: Although the incidence in the cohort overall was only 0.78 per 100 PY, nine risk variables were associated with an HIV incidence of 2 per 100 PY or greater. Stepwise inclusion of these variables revealed a 'high-incidence' subgroup of men representing 24% of the total follow-up time with a combined HIV incidence of 2.71 per 100 PY, who reported at least one of three risk factors in the past 6 months. These men were more willing than others to participate in vaccine and antiretroviral therapy HIV prevention trials.
CONCLUSIONS: These findings demonstrate that it is possible to identify high HIV incidence subpopulations in low-incidence settings such as Australia, and these men are of above average willingness to participate in HIV prevention trials.