Background In subSaharan Africa, HSV-2 infection is common, and increases risk of HIV transmission and acquisition. Tenofovir gel applied before and after vaginal intercourse provided partial protection from HSV-2 acquisition in the CAPRISA 004 study. We enrolled women in a 5-arm, randomised, double-blind, placebo-controlled trial assessing the safety and efficacy of daily use of oral tenofovir, oral tenofovir-emtricitabine, and 1% vaginal tenofovir gel as HIV PrEP, and assessed characteristics of women with baseline HSV and risk of HSV seroincidence during the study.

Methods From September 2009-June 2011, 12,379 women were screened at 15 sites in South Africa, Uganda, and Zimbabwe. Eligibility criteria included normal renal, hematologic and hepatic function, report of vaginal intercourse in prior 3 months, negative pregnancy test, and willingness to use effective contraception throughout. Testing for HSV-2 type-specific antibody (Focus HerpeSelect EIA) was performed on plasma from enrollment and study exit.

Results Of 5,029 participants, baseline HSV serology was available for 4996 (99.3%). Most were from Durban (62%), followed by Johannesburg (14%), Zimbabwe (13%), Uganda (6%), and Klerksdorp (5.2%). Mean age was 25.3 years; 79% were unmarried. Over follow-up of 5,511 person years, end-of-study retention was 91%. Using a cutoff index value of > 3.5, 46% of participants were HSV-2 and 95% HSV-1 seropositive at enrollment. Country- and age-specific HSV-2 seroprevalence ranged from 32% (Zimbabwe) to 63% (Uganda). Seroincidence of HSV-2 by arm will be presented.

Conclusions In this population of women at risk for HIV-1, seroprevalence of HSV-2 was high, with potentially important differences by age and site of enrollment.