Objectives: To evaluate the effect of hormonal contraception including combined oral contraceptives (COCs), and the injectable progestins depo-medroxyprogesterone acetate (DMPA) and norethisterone enanthate (Net-En) on the risk of HIV acquisition among women in South Africa.
Design/methods: We analyzed data from 5567 women aged 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 hormonal contraception exposure on HIV acquisition risk among women overall and among young women (16–24 years) in particular.
Results: Two hundred and seventy 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 nonhormonal contraceptive groups, respectively (P = 0.09). The adjusted hazard ratios (AHRs) were 0.84 [95% confidence interval (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 nonhormonal group controlling for covariates. Age modified the effect of hormonal contraception on HIV acquisition risk; among young women, the AHRs 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% CI0.78–2.35) for Net-En users.
Conclusions: 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.
aFHI 360, Durham, North Carolina
bMemorial Sloan-Kettering Cancer Center, New York
cPopulation Council, New York, USA
dAcademic Medical Center of the University of Amsterdam and Amsterdam Institute for Global Health and Development, Amsterdam, The Netherlands
eUniversity of Cape Town
fUniversity of Limpopo Medunsa Campus
gMedical Research Council, Durban, South Africa
hUniversity of Helsinki, Helsinki, Finland.
Correspondence to Charles S. Morrison, PhD, FHI 360, Durham, NC 27713, USA. Tel: +1 919 544 7040/11472; fax: +1 919 544 7261; e-mail: email@example.com
Received 13 July, 2011
Revised 14 November, 2011
Accepted 23 November, 2011