Challenges in assessing associations between hormonal contraceptive use and the risks of HIV-1 acquisition and transmission

Prior observational studies produced inconsistent findings regarding hormonal contraception (HC) and risks of HIV acquisition and transmission. Heffron et al. conducted secondary data analyses on 3790 HIV discordant couples enrolled in two studies (a randomized trial of HSV-2 suppression and a study of immune correlates of HIV-1 protection) to assess HIV-1 acquisition and transmission in relation to HC use in females. HIV incidence among female HC nonusers was 3.8/100 person years (py), compared to 6.9/100 py among injectable users (p = 0.04) and 5.9/100 py in oral contraceptive users (p = 0.33). Among men, HIV incidence was 1.5/100 py in partners of HIV-positive HC nonusers, compared to 2.6/100 py in partners of injectable users (p < 0.05) and 2.5/100 py in men whose HIV-infected partners used oral contraceptives (p = 0.31). Study strengths included frequent follow up, excellent retention, known HIV exposure and viral load in the index infected partner, genetic linkage of virus from both partners and sexual behavior information. However, confounding by factors that cannot be controlled, including misreporting of condom use, is likely, given participants' high pregnancy rates. Clinicians and clients need to balance potential HC risks with the known risks of unwanted pregnancies. Condom use remains essential for HIV prevention regardless of other contraceptive usage.