ACQUISITION OF HIV AND GENITAL TRACT INFECTION AMONG INJECTABLE PROGESTIN CONTRACEPTION USERS IN SOUTH AFRICA: A PROSPECTIVE COHORT STUDY
Noguchi, Lisa Miyako
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Background Effective contraception contributes substantially to reduced risk for maternal mortality. Some observational studies have noted increased HIV acquisition among women using injectable progestin contraceptives (IPC), particularly depot medroxyprogesterone acetate (DMPA) compared to women not using hormonal contraception (HC). Whether DMPA and another common but different IPC, norethisterone enanthate (NET-EN), confer different risk of HIV and genital tract infection remains relatively unexplored. Methods We analyzed prospective data from 3,316 South African injectable contraception users enrolled in the VOICE study. Cox proportional hazards models were used to compare DMPA and NET-EN users’ HIV risk, adjusting for demographic and behavioral factors. We used Andersen-Gill proportional hazards models to compare DMPA and NET-EN users’ risk for infection with Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), bacterial vaginosis (BV), and Trichomonas vaginalis. Results During 2,734 person-years (py) of follow-up, 207 incident HIV infections were detected (HIV incidence: 7.6/100 py, 95% CI 6.6 to 8.7/100 py). Users of DMPA had higher HIV incidence (8.7/100 py, 95% CI 7.4 to 10.2/100 py), compared to NET-EN users (5.6/100 py, 95% CI 4.3 to 7.2/100 py) (hazard ratio [HR]: 1.58, 95% CI 1.16 to 2.15, p=0.004). This association persisted in the adjusted model (adjusted HR [aHR] 1.46, 95% CI 1.10 to 1.95, p=0.01). However, DMPA and NET-EN users did not differ in acquisition of CT, NG, or trichomonas. Incident BV was lower among DMPA compared to NET-EN users (aHR 0.86, 95% CI 0.75 to 0.98, p=0.02). Conclusions In this prospective cohort of South African IPC users, DMPA was associated with a higher risk of HIV acquisition, compared to NET-EN. This observed difference in HIV-1 risk did not appear to be explained by differential risk for genital tract infection. Our findings are the first to propose that BV acquisition may differ between DMPA and NET-EN users. Most observational data suggest no increased risk for HIV-1 or genital tract infection specific to NET-EN, an equally effective IPC. If these findings are confirmed in other datasets with well-characterized contraceptive exposures, consideration should be given to preferential prescription of NET-EN over DMPA in high HIV-1 incidence settings where NET-EN is available.