While the TDF2 (15) and Partners PrEP (14) studies indicate that oral PrEP can work in women, other trials in high-risk women (FEM-PrEP and VOICE) showed no efficacy (20, 21). This lack of efficacy was largely attributed to poor adherence (22). However, other factors such HIV subtype exposure, mode of transmission, and the percent of stable serodiscordant couples argue that more accurate estimates of oral PrEP for women at high risk in southern Africa are needed (23). Oral PrEP is less forgiving to lapses in dosing in women compared to men. Heterosexual women and transgender men engaging in vaginal sex must take PrEP every day for effective protection against HIV (19). The difference in oral PrEP protection in men versus women may be explained by pharmacodynamic differences where 100-fold lower-levels of the active form of tenofovir is present in genital tissues of women versus rectal tissue (24).