Date Published: February 2, 2017
Publisher: Public Library of Science
Author(s): Anneli Uusküla, Mait Raag, Kristina Marsh, Ave Talu, Sigrid Vorobjov, Don Des Jarlais, Javier R. Lama.
New injectors / younger drug users are an important population to target for intervention because they are often at especially high risk of HIV and HCV infection. We examined HIV prevalence and gender differences in HIV prevalence and risk behavior among new injection-drug-users in Tallinn, Estonia.
Respondent driven sampling (RDS) interview surveys and HIV testing were conducted in Tallinn in 2009, 2011 and 2013. We classified “new injectors” as persons who reported their first injection as occurring within three years of the study interview. Recruiting trees of the three individual RDS studies were joined to form one RDS dataset and RDS estimates for prevalence and means were derived. Bootstrap tests were used to compare data from men and women, HIV infected and uninfected.
Among 110 new injectors (34 women and 76 men) the mean age was 24.5 (SD 7.5) years; 63% reported injecting mainly fentanyl, 34% injecting mainly amphetamine, 36% sharing syringes, 89% were sexually active, and, of these, 88% did not always use condoms in the last 6 months. HIV prevalence was 18% (95%CI 8–28%) (41% (95%CI 19–63%) among female and 7% (95%CI 2–12%) among male new injectors). Based on self-reports, 8.1% of all new injectors (and 22% of female new injectors) were HIV positive before starting to inject drugs. 40% of HIV infected reported receiving antiretroviral therapy. In multivariable analysis, gender (male: OR 0.12, 95% CI 0.03–0.45), main drug injected (fentanyl: OR 6.7, 95% CI 1.3–35.7) and syringe sharing (distributive: OR 0.11, 95% CI 0.02–0.55; and receptive: OR 3.7, 95% CI 1.0–13.5) were associated with the HIV seropositivity.
New injectors exhibit high-risk behavior and correspondingly high HIV prevalence. Sexual transmission of HIV infection, including before injection initiation, is likely to be a significant contributor to HIV risk among female new injectors. This highlights the need to identify and target new injectors and their partners with gender specific interventions in addition to interventions to reduce initiation into injecting and ensuring provision of ART to HIV positive new injectors.
Young people aged 15–24 years accounted for an estimated 35% of all new HIV infections in 2012 . Those who have recently begun injecting illicit drugs (“new injectors”) are typically young, engage in very high rates of injecting and sexual risk behavior [2–5], and are relatively unlikely to engage in evidence-based prevention initiatives such as needle syringe programs (NSP), medically assisted drug treatment (MAT) or antiretroviral therapy (ART) . Because of these factors, new injectors are at especially high risk of acquiring hepatitis C (HCV) infection in almost all illicit drug-injecting populations [7,8] and are also at great risk of acquiring HIV in areas of high HIV prevalence. It has also been suggested that sexual behavior patterns may contribute to HIV transmission among new injectors [9–11].
Estonia is a small country in the north-eastern part of Europe with a population of about 1,340,000 . A very rapid HIV epidemic occurred in Estonia in 2000, and although HIV incidence has gradually decreased since the peak in early 2000s (from 108.0 / 100 000 in 2001  to 20.6 in 2014 ), by 2014 Estonia still had the third highest per capita HIV incidence in Europe (22.1 / 100 000), after Ukraine (36.9 / 100 000) and Russia (58.4 / 100 000 in 2014) .
We defined “new injectors” as people who reported their first injection as occurring within three years of the study interview. Studies using duration of injecting typically define new injectors as people injecting of up to 3 years or less than 5 years . The DUIT study, which is the largest interventional study to date on prevention of HCV infection, used a cut-off age of 30 for “young injectors” . The overlap between chronological age (< 30 years) and short duration of injecting drugs (the first injection occurring within three years of the study interview) among our subjects was 90%, therefore our results may be compared with other studies with slightly differing definitions of new / young injectors. From the total sample of current IDUs (n = 325 in 2009, n = 349 in 2011, and n = 328 in 2013), 14% (n = 109) were new injectors (34 women and 75 men). The proportion of new female injectors among all new injectors varied from 18% in 2009 to 44% in 2013 (sample proportions). Data on study sample characteristics of the study sample (by year and gender) are presented in Fig 1. Overall, the crude estimates (sample proportions) did not significantly differ from the RDS adjusted estimates, nor were there clear trends in estimates over the years 2009, 2011 and 2013 in the selected variables (Fig 1). Estimates for homophily indexes for key variables in the study sample were close to zero, suggesting a single underlying population for each sample (Table 1). Estimates for homophily indexes for both new and long term injectors were close to zero, suggesting a single underlying population for each group. This study documented a high HIV prevalence among new injectors in Tallinn (one fifth of people reporting injecting drugs for less than three years were HIV infected) and corresponding high self-reported rates of risk behaviors (35% reported sharing syringes/needles and 86% unprotected sex). Our findings of high HIV prevalence and high rates of risk behavior among new injectors are in agreement with reports from other sites ( Dar es Salaam;  Ukraine; [42,43] USA), as is HIV seropositivity being associated with injection equipment sharing and fentanyl as a main injection drug used [24,26]. New injectors / younger drug users are an important target for additional interventions because they are often at high risk of acquiring HIV and HCV. There is a need for focused gender-specific HIV strategies for women, men, and new/young injectors in addition to interventions to reduce initiation into injecting and ensuring provision of ART to new injectors who are HIV positive. Source: http://doi.org/10.1371/journal.pone.0170956