Oral pre-exposure prophylaxis (PrEP) against HIV infection has demonstrated efficacy in men who have sex with men, serodiscordant couples, and young heterosexuals; however, efficacy was not shown in two studies of women. Lack of adherence is the leading hypothesis for these discrepant findings. Adherence outside of rigorous clinical trials is unknown and is essential to know in order to determine whether PrEP will be an effective public health strategy. The proposed study will determine if HIV-uninfected people in serodiscordant couples outside a clinical trial will adhere adequately enough to PrEP to be protected against HIV transmission. Approach: This study builds on our experience conducting the Adherence Sub-study within the Partners PrEP Study (a phase III clinical trial of tenofovir and emtricitabine/tenofovir PrEP) and will be integrated into a recently funded study of a public health delivery model of antiretroviral therapy-based HIV prevention strategies involving 500 serodiscordant couples in Uganda and Kenya (R01MH095507, PI: Baeten).
Our Specific Aims are a follows: 1) Assess the level, trajectory, and correlates of PrEP adherence in research-naive discordant couples receiving PrEP in a public health delivery model with adherence counseling practical for scale-up; 2) Determine the relationship between patterns of adherence and risk exposure outside of a clinical trial; and 3) Determine if the level and patterns of real world adherence and risk exposure determined in Aims 1 and 2 substantially alter current estimates of PrEP effectiveness and cost-effectiveness. Innovation: We will: 1) characterize PrEP adherence in serodiscordant couples recruited into a demonstration project of PrEP delivery involving limited adherence counseling that is practical for scale-up settings; 2) use a novel conceptual framework to understand PrEP adherence behavior; 3) use text message reports of sexual behavior combined with electronic adherence monitoring to characterize temporal patterns of sexual exposure and PrEP adherence; and 4) develop models of the tenofovir drug concentration-time relationship, using prospectively collected samples, which can be used to determine which patterns of adherence are likely adequate for protection against HIV infection. Investigators: Dr. Jessica Haberer is a new investigator with significant experience studying adherence to antiretroviral therapy and PrEP in sub-Saharan Africa. Her team includes expertise in clinical epidemiology (Drs. Jared Baeten and Connie Celum), adherence measurement (Dr. David Bangsberg), qualitative analysis (Dr. Norma Ware), tenofovir pharmacokinetic modeling (Drs. Craig Hendrix and Ayyappa Chaturvedula), statistical analysis (Dr. Deborah Donnell), cost-effective modeling (Dr. Tim Hallett), and sub-Saharan African research experience (Drs. Nelly Mugo and Elly Katabira).
Over 2.5 million people are infected with HIV each year. The majority of these new infections occur in sub- Saharan Africa, where up to 20% of couples are serodiscordant (meaning one member is HIV-infected and the other is uninfected). This study will determine if HIV-negative individuals in serodiscordant sexual relationships will adhere adequately enough to PrEP to achieve reliable protection outside of clinical trials with counseling at levels practical for scale up, thereby helping to understand the public health and cost implications for PrEP implementation.
