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The future role of rectal and vaginal microbicides to prevent HIV infection in heterosexual populations: implications for product development and prevention
  1. Marie-Claude Boily1,
  2. Dobromir Dimitrov2,
  3. Salim S Abdool Karim3,
  4. Benoît Mâsse2,4
  1. 1Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK
  2. 2Vaccine & Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
  3. 3CAPRISA: Centre for the AIDS Program of Research in South Africa, University of KwaZulu-Natal, Durban, South Africa
  4. 4CHU Sainte-Justine Research Centre, University of Montreal, Montreal, Quebec, Canada
  1. Correspondence to Dr Marie-Claude Boily, Department of Infectious Disease Epidemiology, Imperial College London, St Mary's Campus, Norfolk Place, Paddington, London W2 1PG, UK; mc.boily{at}


Objectives To compare the potential impact of rectal (RMB), vaginal (VMB) and bi-compartment (RVMB) (applied vaginally and protective during vaginal and anal intercourse) microbicides to prevent HIV in various heterosexual populations. To understand when a RMB is as useful than a VMB for women practicing anal intercourse (AI).

Methods Mathematical model was used to assess the population-level impact (cumulative fraction of new HIV infections prevented (CFP)) of the three different microbicides in various intervention scenarios and prevalence settings. We derived the break-even RMB efficacy required to reduce a female's cumulative risk of HIV infection by the same amount than a VMB.

Results Under optimistic coverage (fast roll-out, 100% uptake), a 50% efficacious VMB used in 75% of sex acts in population without AI may prevent ∼33% (27, 42%) new total (men and women combined) HIV infections over 25 years. The 25-year CFP reduces to ∼25% (20, 32%) and 17% (13, 23%) if uptake decreases to 75% and 50%, respectively. Similar loss of impact (by 25%–50%) is observed if the same VMB is introduced in populations with 5%–10% AI and for RRRAI=4–20. A RMB is as useful as a VMB (ie, break-even) in populations with 5% AI if RRRAI=20 and in populations with 15%–20% AI if RRRAI=4, independently of adherence as long as it is the same with both products. The 10-year CFP with a RVMB is twofold larger than for a VMB or RMB when AI=10% and RRRAI=10.

Conclusions Even low AI frequency can compromise the impact of VMB interventions. RMB and RVMB will be important prevention tools for heterosexual populations.

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  • Funding DD and BM are supported by a grant from the National Institutes of Health (Grant number 5 U01 AI068615-03).

  • Competing interests None.

  • Provenance and peer review Commissioned; externally peer reviewed.