Daily Tenofovir-Containing PrEP Ineffective Among Women in Africa Due to Low Adherence

Summary and Comment |
February 4, 2015

Daily Tenofovir-Containing PrEP Ineffective Among Women in Africa Due to Low Adherence

  1. Salim S. Abdool Karim, MD, PhD

Daily oral and topical tenofovir-containing pre-exposure prophylaxis was shown to be ineffective in preventing new HIV infections.

  1. Salim S. Abdool Karim, MD, PhD

Daily oral pre-exposure prophylaxis (PrEP) and pericoital vaginal tenofovir gel have been shown to prevent HIV infection in some groups. The Vaginal and Oral Interventions to Control the Epidemic (VOICE) trial assessed whether daily treatment with oral tenofovir disoproxil fumarate (TDF), oral TDF/FTC, or vaginal 1% tenofovir gel could prevent new HIV infections among women in South Africa, Uganda, and Zimbabwe.

None of the regimens proved effective. HIV-infection incidence per 100 person-years — 5.7 overall (n=4947) — was 49% higher (P=0.07) in the TDF group, 4% higher (P=0.81) in the TDF/FTC group, and 15% lower (P=0.37) in the tenofovir gel group than in the placebo group. Although adherence was 90% by self-reports and 86% by returned-product counts, it was ≤30% based on detection of tenofovir in plasma; in all three groups, ≥50% of the women had no plasma tenofovir detected at any quarterly visit. Incidence was significantly lower in women with detectable plasma tenofovir at the first quarterly visit than in those without (1.9 vs. 6.1; P=0.02). Age ≥25, being married, and being multiparous were associated with higher likelihood of PrEP adherence. The drug regimens were safe, although mildly elevated serum creatinine levels were more common in the TDF/FTC group than in the placebo group (1.3% vs. 0.2%; P=0.004).

Comment

The VOICE trial findings, although disappointing, highlight the need to better understand the motivations of healthy HIV-uninfected individuals who volunteer to participate in HIV-prevention trials. Because PrEP effectiveness depends on both drug efficacy and regimen adherence, the results are not surprising: Fewer than half the study participants took any of their prescribed drugs. The high HIV-acquisition rate seen in this trial highlights the urgent need among young women in Africa for HIV-prevention strategies that are less dependent on adherence.

Editor Disclosures at Time of Publication

  • Disclosures for Salim S. Abdool Karim, MD, PhD at time of publication Consultant / Advisory board Merck, Sharpe & Dohme Editorial boards HIV and Infectious Diseases; Open Journal of Virology; eLife; The Lancet Global Health; AIDS Reviews Grant / Research support National Institutes of Health/NIAID; CDC/PEPFAR; Tides Foundation/MAC AIDS Fund; Howard Hughes Medical Institute; WHC/Technology Innovation Agency; UCT/TIA; CONRAD/USAID

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