HIV among people who inject drugs in Stockholm - prevalence, incidence and treatment outcomes

Background: People who inject drugs (PWID) are at high risk of HIV transmission through sharing of injection equipment. Needle and syringe programs (NSP) prevent the spread of HIV and are important arenas for reaching and maintaining the 95-95-95 UNAIDS HIV targets among PWID. To date, HIV prevalence, incidence and the continuum of care among PWID have been scarcely studied in Sweden.
Methods: All participants at the Stockholm NSP, year 2013 to 2023, were HIV tested at first visit and every 3-6 month in the program. Demographic data and data on drug use, HIV treatment and causes of death were registered in the national NSP quality register. 
Results: Between April 2013 and April 2023, 4.4% (200/4513) of all PWID enrolled in the Stockholm NSP tested positive for HIV. The average age at enrollment was 44.9 years. 23% were women. 46% injected amphetamine, 39% heroin and 32% had opioid agonist treatment at some point. Mean follow-up time in the NSP was 4.6 years. 
The annual HIV prevalence decreased over time from 8.6% to 5.7% (p<0.01). We noted a total of 17 incident HIV cases among NSP participants who had a negative HIV test at enrollment and the overall HIV incidence over time was 0.15/100 PY (95% CI 0.1-0.3). In addition, we diagnosed 25 new HIV cases at first visit to the NSP, of which 15 were undiagnosed new cases and 10 were known cases previously diagnosed abroad. 92% (183/200) had a registered HIV treatment in the NSP quality register, of which 39% received HIV treatment at some point on site, at the NSP. Among those with treatment, and with a follow-up HIV RNA sample, 84% had HIV RNA <20 copies/mL at the last visit to the NSP. 
During the study period, 23.5% (n=47) of HIV participants died compared to 14.4% among those without HIV (p<0.001). Participants with HIV died at an older age compared to those without HIV, 53 vs. 43 years. However, only three participants had HIV as the major cause of death. Overdoses and other external causes, including suicide and accidents, were the most common causes of death. 
Conclusion: This study is the first 10-year follow-up of PWID living with HIV and enrolled in an NSP in Sweden. The study shows a continuously low HIV incidence and a prevalence that decreases over time. The NSP has been important for finding new cases of HIV among PWID in Stockholm, both in terms of new incident cases and known cases that have recently moved to Stockholm from abroad. The NSP has facilitated the HIV continuum of care for the vast majority of HIV positive PWID with access to ART treatment through the Infection Diseases Clinics or on site at the NSP. Mortality was more frequent among PWID living with HIV compared to those without HIV, which needs to be studied further.