Risk factors for HIV incidence in women participating in an HSV suppressive treatment trial in Tanzania

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Abstract
Objectives: A randomized, double-blind, placebo-controlled trial (RCT) of herpes simplex virus type 2 suppressive therapy with acyclovir 400 mg twice daily conducted among women in northwestern Tanzania reported a similar rate of HIV acquisition in both trial arms (Current Controlled Trials number ISRCTN35385041). Risk factors for HIV incidence were examined in the context of 3-monthly follow-up visits offering both voluntary counselling and testing and care for sexually transmitted infections. Design: Prospective cohort analysis of trial participants enrolled and followed for up to 30 months. Methods: Risk factors for HIV acquisition were analysed using Cox regression. Results: Overall, 821 herpes simplex virus type 2 seropositive, HIV seronegative women were randomized; 400 randomized to acyclovir and 421 to placebo; 659 (80.3%) completed follow-up. HIV incidence was 4.27 per 100 person-years. There was no overall impact of acyclovir on HIV incidence [hazard ratio = 1.01; 95% confidence interval (CI) 0.61–1.66]. HIV acquisition was independently associated with younger age at enrolment (age 16–19 vs. 30–35: hazard ratio = 4.02; 95% CI 1.67–9.68), alcohol consumption at enrolment (≥30 drinks/week vs. none: hazard ratio = 4.39, 95% CI 1.70–11.33), having paid sex within the previous 3 months (hazard ratio = 1.82, 95% CI 1.09–3.05), recent infection with gonorrhoea (hazard ratio = 3.62, 95% CI 1.62–8.08) and injections in the previous 3 months (hazard ratio = 3.45, 95% CI 1.62–7.34). There was some evidence of an association between HIV incidence and living in the recruitment community for less than 2 years (hazard ratio = 1.75, 95% CI 0.98–3.10) and exposure to hormonal contraception (hazard ratio = 1.60, 95% CI 0.93–2.76). Conclusion: A high incidence of HIV was observed in this trial cohort, especially in young women. Interventions are needed to address the risk associated with alcohol use and to sustain control of other sexually transmitted infections.