HPTN Modelling Center Plenary
Introducing HPTN Modelling Centre: Who? What? When? How?
Modelling HIV Transmission and Treatment for US MSM to Estimate the Impact of HPTN 078 on HIV Incidence.
Kate M. Mitchell
Predicting the individual-level effectiveness of daily and non-daily PrEP based on study results from HPTN 067 ADAPT
Abstract: HPTN 067 evaluated the feasibility of daily and two non-daily PrEP regimens among women in South Africa and men who have sex with men (MSM), and transgender women, in Thailand and US. The study was designed to assess differences in acceptability and adherence to different PrEP regimens but not differences in HIV incidence across arms. We have used an individual-based mathematical model to compare the predicted reduction in HIV incidence under different dosing regimens using detailed sexual activity data from each trial site. A sex act was assumed ”PrEP protected” if a PrEP dose was taken within 2 days before the act and another dose was taken within 1 day after the act. A sex act was assumed “semi-protected” if only one of the two doses were taken. We also consider how the assumed PrEP efficacy during PrEP protected sex acts influences modelling predictions. Our analysis suggests that non-daily PrEP is unlikely to be as effective as daily PrEP in reducing HIV incidence among females in South Africa and among MSM in the USA and Thailand due to higher proportions of sex acts reported to be protected by PrEP with daily use. The comparison across the three sites suggests that PrEP was most effective among MSM in Thailand whereas the success of PrEP interventions among women in South Africa or MSM in the USA may depend on the PrEP efficacy for semi-protected acts.