Objectives
Data are limited on the potential impact of the injectable progestin contraceptives (IPC) norethisterone enanthate on risk of vaginal infections. We assessed whether users of two common IPC (depot medroxyprogesterone acetate [DMPA] and norethisterone enanthate [NET-EN]) differed in their risk for bacterial vaginosis (BV) and Trichomonas vaginalis (TV).
Methods
We conducted a secondary analysis of IPC users enrolled at South African sites in VOICE, a multi-center randomized trial of topical and oral HIV-1 chemoprophylaxis. BV was diagnosed in a central laboratory using Nugent criteria and TV by OSOM Rapid Trichomonas® test, with testing at enrollment, annually, and as clinically indicated. Separate Andersen-Gill proportional hazards regression analyses were used to compare risk for BV and TV between DMPA and NET-EN users, with adjustment for potential confounders, including baseline age and HSV-2 serology; and time-varying recent partner change, concurrent combined oral contraceptive use, douching, frequency of sex, metronidazole treatment and condom use over the course of follow-up.
Methods
We conducted a secondary analysis of IPC users enrolled at South African sites in VOICE, a multi-center randomized trial of topical and oral HIV-1 chemoprophylaxis. BV was diagnosed in a central laboratory using Nugent criteria and TV by OSOM Rapid Trichomonas® test, with testing at enrollment, annually, and as clinically indicated. Separate Andersen-Gill proportional hazards regression analyses were used to compare risk for BV and TV between DMPA and NET-EN users, with adjustment for potential confounders, including baseline age and HSV-2 serology; and time-varying recent partner change, concurrent combined oral contraceptive use, douching, frequency of sex, metronidazole treatment and condom use over the course of follow-up.
Results
Among all 3029 IPC users, 1719 (56.8%) used DMPA, 1058 (34.9%) used NET-EN, and 252 (8.3%) used both types of IPC at different times during follow-up. 2,957 IPC users had follow-up testing for TV. At baseline, the prevalence of either infection did not differ between DMPA and NET-EN users (BV: 39.5% vs. 39.6%, p=0.96; TV: 5.8% vs. 5.0%, p=0.36). Compared to NET-EN users, DMPA users were older (24 vs. 23 years, p<0.001), less likely to report multiple partners (2.7% vs. 5.5%, p<0.001), and more likely to be HSV-2-seropositive compared to NET-EN users (50.9% vs. 39.8%, p<0.001). Incident BV among those negative at baseline was reduced for DMPA compared to NET-EN users after adjusting for potential confounders (aHR 0.86, 95% CI 0.75 to 0.98, p=0.02) (Table 1). However, we observed no difference in incident TV between DMPA and NET-EN users negative for TV at baseline (HR 0.92, 95% CI 0.70-1.20, p=0.54; aHR 1.06, 95% CI 0.78-1.45, p=0.69).
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