New studies presented at the 2016 International AIDS Conference in Durban provide new insights on the use of PrEP among a broad range of populations. One study provided new national estimates of PrEP use in the US by geography and other demographics, another found the near elimination of HIV transmission risk among serodiscordant heterosexual couples using both PrEP and antiretroviral treatment, and two additional studies examined PrEP use among adolescents in both southern Africa and the US.
Research featured in the briefing included:
Increased PrEP use among US adults: A nationally representative study assessing PrEP use in the U.S. found that 49,469 adults received a Truvada prescription for PrEP from January 2013 to December 2015, and that the number of prescriptions increased nationally over time: 3,746 in 2013; 14,756 in 2014; and 30,967 in 2015.
Scott McCallister of Gilead Sciences, the manufacturer of Truvada, presented the study, which included de-identified data from 82% of retail pharmacies on adults who received a Truvada prescription.
Study results also showed that the four states with the highest number of new HIV cases in the US (California, New York, Texas, and Florida) accounted for 43% of PrEP starts. From 2014 to 2015, PrEP starts increased in the South and Northeast, and decreased in the Midwest and West. The vast majority of PrEP prescriptions were for males (87.5%), and the mean age was 37.4 years, with 11.5% under age 25. Compared to HIV-positive individuals, those receiving PrEP were about three times less likely to be female (95% CI 3.0-3.2) and twice as likely to be under age 25 (95% CI 1.93-2.05).
Despite positive trends in utilization, authors conclude that PrEP use must increase to ensure that lifetime HIV risk decreases in areas of high prevalence in the US.
Combination of PrEP and ART leads to near elimination of HIV transmission among serodiscordant couples: Final results from the Partners Demonstration Project, an open-label PrEP and ART delivery study that enrolled treatment-naïve, high-risk, heterosexual HIV serodiscordant couples from Kenya and Uganda, found that integrated use of PrEP and ART nearly eliminated HIV transmission within these couples. Of 1,013 couples enrolled, 67% had an HIV-positive female partner; median age was 29.
Among a randomly selected sample of HIV-negative partners receiving PrEP, tenofovir was detected in 82% of plasma samples (483/587 visits). Treatment was initiated by 92% of HIV-positive partners by 24 months, and viral suppression (<400 copies/mL) was achieved in 90%. As of January 2016, scientific models predicted that 63 incident HIV infections would be expected (incidence rate 5.1 per 100 person years, 95% CI 3.9-6.4).
However, Jared Baeten of the University of Washington reported that only five incident infections had actually been observed (incidence rate 0.3, 95% CI 0.1-0.7), for a sustained HIV relative risk reduction of 94% (95% CI 85-98, p<0.001). The results show near elimination of HIV risk among a high-risk cohort.
Closer look at PrEP use among adolescents at risk: Plus Pills is the first southern African open-label study to explore the acceptability, safety, and use of oral PrEP among HIV-negative adolescents (ages 15-19 years). Study participants (n=148; 98 female and 50 male) enrolled in two sites, Cape Town and Soweto. Median age of study participants was 18 and median age at sexual debut was 15. Participants were required to take PrEP daily for the first 12 weeks of the study, but could opt out at the 12-week mark and at each 3-month interval thereafter.
At enrolment, participants reported an average of 1.5 weekly sex acts, 30% had two or more partners in the past 12 months, 43% reported infrequent condom use, and 38% tested positive for sexually transmitted infections. Lead author Katherine Gill of the Desmond Tutu HIV Centre discussed the study results, which found no HIV incident infections. At 12 weeks, 72% reported good adherence (>6 pills/week) and 76% had tenofovir plasma levels (>40 ng/ml).
At the 12-week mark, 15% of participants chose to opt out. According to study authors, results showed that early adherence was reasonable among a high-risk adolescent population
A separate open-label study looked at PrEP use among gay and bisexual male adolescents (ages 15-17) in six U.S. cities. While Truvada is not currently licensed for PrEP among individuals under age 18, participants were permitted to autonomously consent to the study. Between August 2013 and September 2014, ATN 113 (Project PrEPare) enrolled 78 individuals (mean age=16.5; 33.3% mixed race, 29.5% black, 20.5% Latino). Sybil Hosek of the Stroger Hospital of Cook County Health and Hospitals System presented the study results. Incident sexually transmitted infections were diagnosed in 12.3% of participants at week 24 and 10.6% at week 48. The HIV seroconversion rate per 100 person-years was 6.41 (95% CI: 4.90-25.87). The majority of participants reported condomless sex throughout the study; no significant associations were found between condomless sex and adherence. While the majority of participants achieved protective drug levels during monthly visits, the study found that adherence decreased with quarterly visits.