HIV Incidence and Risk Factors for Acquisition in HIV Discordant Couples in Masaka, Uganda: An HIV Vaccine Preparedness Study

OBJECTIVES: To determine the incidence of and risk factors for HIV acquisition in a cohort of HIV-uninfected partners from HIV discordant couples in Masaka Uganda and to establish its suitability for HIV vaccine trials. METHODS: HIV-uninfected adults living in HIV discordant couple relationships were enrolled and followed for 2 years. Interviews medical investigations HIV counseling and testing syphilis and urine pregnancy (women) tests were performed at quarterly visits. Sexual risk behaviour data were collected every 6 months. RESULTS: 495 participants were enrolled of whom 34 seroconverted during 786.6 person-years of observation (PYO). The overall HIV incidence rate [95% confidence interval (CI)] was 4.3 [3.1-6]; and 4.3 [2.8-6.4] and 4.4 [2.5-8] per 100 PYO in men and women respectively. Independent baseline predictors for HIV acquisition were young age [18-24 (aRR = 4.1 95% CI 1.6-10.8) and 25-34 (aRR = 2.7 95% CI 1.2-5.8) years]; alcohol use (aRR = 2.6 95% CI 1.1-6); and reported genital discharge (aRR = 3.4 95% CI 1.6-7.2) in the past year. Condom use frequency in the year preceding enrolment was predictive of a reduced risk of HIV acquisition [sometimes (aRR = 0.4 95% CI 0.2-0.8); always (aRR = 0.1 95% CI 0.02-0.9)]. In the follow-up risk analysis young age [18-24 (aRR = 6.2 95% CI 2.2-17.3) and 25-34 (aRR = 2.3 95% CI 1.1-5.0) years] reported genital discharge (aRR = 2.5 95% CI 1.1-5.5) serological syphilis (aRR 3.2 95% CI 1.3-7.7) and the partner being ART naive (aRR = 4.8 95% CI 1.4-16.0) were independently associated with HIV acquisition. There were no seroconversions among participants who reported consistent condom use during the study. CONCLUSIONS: The study has identified important risk factors for HIV acquisition among HIV discordant couples. HIV-uninfected partners in discordant couples may be a suitable population for HIV vaccine efficacy trials. However recent confirmation that ART reduces heterosexual HIV transmission may make it unfeasible to conduct HIV prevention trials in this population.