Potential impact and cost-effectiveness of condomless-sex-concentrated PrEP in KwaZulu-Natal accounting for drug resistance.

INTRODUCTION: Oral pre-exposure prophylaxis (PrEP) in the form of tenofovir-disoproxil-fumarate/emtricitabine is being implemented in selected sites in South Africa. Addressing outstanding questions on PrEP cost-effectiveness can inform further implementation. METHODS: We calibrated an individual-based model to KwaZulu-Natal to predict the impact and cost-effectiveness of PrEP, with use concentrated in periods of condomless sex, accounting for effects on drug resistance. We consider (i) PrEP availability for adolescent-girls-and-young-women (aged 15-24; AGYW) and female sex workers (FSW), and (ii) availability for everyone aged 15-64. Our primary analysis represents a level of PrEP use hypothesized to be attainable by future PrEP programmes. RESULTS: In the context of PrEP use in adults aged 15-64 there was a predicted 33% reduction in incidence, and 36% reduction in women aged 15-24. PrEP was cost effective, including in a range of sensitivity analyses, although with substantially reduced (cost) effectiveness under a policy of ART initiation with efavirenz- rather than dolutegravir-based regimens due to PrEP undermining ART effectiveness by increasing HIV drug resistance. CONCLUSIONS: PrEP use concentrated during time periods of condomless sex has the potential to substantively impact HIV incidence and be cost-effective.