Combined prevention for persons who inject drugs in the HIV epidemic in a transitional country: the case of Tallinn, Estonia

The study was undertaken to assess the potential effectiveness of combined HIV prevention on the very high seroprevalence epidemic among persons who inject drugs (PWID) in Tallinn, Estonia, a transitional country. Data from community-based cross-sectional (respondent-driven sampling) surveys of PWID in 2005, 2007, 2009, and 2011 were used together with mathematical modeling of injection-associated HIV acquisition to estimate changes in injection-related HIV incidence during these periods. Utilization of one, two, or three of the interventions available in the community (needle and syringes exchange program, antiretroviral treatment [ART], HIV testing, opioid substitution treatment) was reported by 42.5%, 30.5%, and 11.5% of HIV+ and 34.7%, 36.4%, and 5.7% of HIV- PWIDs, respectively, in 2011. The modeling results suggest that the combination of needle/syringe programs and provision of ART to PWID in Tallinn substantially reduced the incidence of HIV infection in this population, from an estimated 20.7/100 person-years in 2005 to 7.5/100 person-years in 2011. In conclusion, combined prevention targeting HIV acquisition and transmission-related risks among PWID in Tallinn has paralleled the downturn of the HIV epidemic in this population.