To evaluate the effect of hormonal contraception (HC) including combined oral contraceptives (COC), and the injectable progestins depo-medroxyprogesterone acetate (DMPA) and norethisterone enanthate (Net-En) on the risk of HIV acquisition among women in South Africa.
We analyzed data from 5567 women ages 16–49 years participating in the Carraguard Phase 3 Efficacy Trial. Participants were interviewed about contraceptive use and sexual behaviors and underwent pelvic examinations and HIV testing quarterly. We used marginal structural Cox regression models to estimate the effect of HC exposure on HIV acquisition risk among women overall and among young women (16–24 years) in particular.
270 participants became HIV-infected (3.7 per 100 woman-years); HIV incidence was 2.8, 4.6, 3.5 and 3.4 per 100 woman-years in the COC, DMPA, Net-En and non-hormonal contraceptive groups, respectively (P=0.09). The adjusted hazard ratios (AHR) were 0.84 (95% CI 0.51–1.39), 1.28 (95% CI 0.92–1.78) and 0.92 (95% CI 0.64–1.32) among COC, DMPA and Net-En users, respectively, compared with the non-hormonal group controlling for covariates. Age modified the effect of hormonal contraception on HIV acquisition risk; among young women, the adjusted HRs were 1.02 (95% CI 0.46–2.28) for COCs, 1.68 (95% CI 0.96–2.94) for DMPA and 1.36 (95% CI 0.78–2.35) for Net-En users.
In this study conducted among South African women, hormonal contraception did not significantly increase the risk of HIV acquisition. However, the effect estimate does not rule out a moderate increase in HIV risk associated with DMPA use found in some other recent studies.