Objective: To evaluate the effect of oral and injectable hormonal contraception on the risk of HIV acquisition among women in South Africa and Zimbabwe.
Design: Secondary data analysis of 4913 sexually active women aged 18–49 years followed for up to 24 months in the Methods for Improving Reproductive Health in Africa (MIRA) phase III effectiveness trial of the diaphragm and lubricant gel for HIV prevention.
Methods: Participants were interviewed quarterly about contraception and sexual behavior and were tested for pregnancy, HIV, and other sexually transmitted infections. We used a Cox proportional hazards marginal structural model, weighted by the inverse probability of hormonal contraception use, to compare the risk of HIV acquisition among nonpregnant women reporting use of combined oral contraceptive pills (COC), progestin-only pills (POP), and/or injectable hormonal contraception to women not using these methods.
Results: During the study, 283 participants seroconverted. Use of oral contraceptives (POP or COC) was not associated with HIV risk [adjusted hazard ratio (HRa) = 0.86, 95% confidence interval (CI) 0.32, 1.78]. Injectable hormonal contraception was associated with a small nonsignificant risk of HIV infection (HRa = 1.34, 95% CI 0.75, 2.37). The effect of injectable hormonal contraception was similar in the unweighted site-adjusted only (HRa = 1.32, 95% CI 1.00, 1.74) and baseline factor adjusted models (HRa = 1.27, 95% CI 0.94, 1.72).
Conclusions: In this study, oral contraceptives were not associated with HIV acquisition. There is substantial uncertainty in the effect of injectable hormonal contraception on HIV risk. These findings underscore the importance of dual protection with condoms and the need for diverse contraceptive options for women at risk of HIV infection.