Background: Scale-up of HIV testing, antiretroviral therapy and PrEP access in South Africa has prompted anticipation of a national decrease in HIV incidence. The 2017 South African National household-based HIV Prevalence, Incidence, Behaviour and Communication Survey reported decreased national HIV incidence, including among women aged 15-49 years (estimate 0.93 per 100 woman-years from 2.28 in 2015). We conducted a prospective clinical trial among women in South Africa between 2015 and 2018 and measured HIV incidence.
Methods: ECHO included sexually active, HIV-negative women aged 16-35 years, seeking effective contraceptives and willing to be randomised to intramuscular depot medroxyprogesterone acetate, copper intrauterine device, or levonorgestrel implant. Women were followed for 12-18 months across 9 sites in South Africa, plus three in Kenya, the Kingdom of Eswatini and Zambia. HIV incidence based on prospectively observed HIV seroconversions and exact 95%CIs based on a Poisson distributions assumption were assessed. Cox proportional hazards regression models were used to define cofactors related to incident HIV.
Results: Of 7829 women enrolled, 5768 women aged 18-35 were enrolled in South Africa and contributed 7647 woman-years of follow-up. The median age was 23 and 62.5% were ≤24 years. A total of 345 incident HIV infections occurred, for an incidence of 4.51 per 100 woman-years of follow-up (95%CI 4.05-5.01). Incidence was >3.30 per 100 woman-years at all South African sites, the largest being 6.80 per 100 woman-years (Table). In multivariable models, age ≤24 years, baseline infection with sexually transmitted infections (HSV-2, gonorrhea or chlamydia), BMI≤30, and having new or multiple partners were all strongly associated with HIV incidence.
Conclusions: HIV incidence was high among young South African women enrolled in a prospective study between 2015 and 2018. Provision of diverse prevention options are needed to mitigate ongoing risks of HIV acquisition for this population.

SiteEnrolled (n)HIV seroconversions (n)Woman-years of follow-upHIV incidence per 100 woman-yearsLower boundUpper bound
Cape Town56031703.824.402.996.25
East London61444819.455.373.907.21
[Table 1: HIV Seroincidence in South African Sites]