Sustained effect of Scotland's HIV pre-exposure prophylaxis programme on transmission among gay and bisexual men who have sex with men: Population-based retrospective cohort study.

OBJECTIVES

To evaluate the population-level impact of seven years of Scotland's HIV pre-exposure prophylaxis (PrEP) programme among gay, bisexual and other men who have sex with men (GBMSM).

METHODS

National administrative data were used to estimate PrEP coverage and HIV incidence among 35 342 GBMSM attending specialist sexual health services between July 2015 and March 2024. Poisson regression was used to investigate the risk of HIV acquisition and its association with the extent of PrEP prescribing.

RESULTS

PrEP coverage increased from 21% in the initial PrEP period (July 2017 to March 2020) to 45% in the latter period (April 2022 to March 2024). HIV incidence reduced from 4.46 per 1000 person-years in the pre-PrEP period (July 2015 to June 2017) to 1.66 in the initial PrEP period (aIRR 0.37, 95% CI 0.25-0.54) and remained stable thereafter. During the entire PrEP period, the risk of HIV acquisition was reduced among those 'currently prescribed' (involving 4 HIV acquisitions among 11 720 person-years) compared to those never prescribed (60 HIV acquisitions among 34 328 person-years) (aIRR 0.19, 95% CI 0.07-0.51). Compared to those currently prescribed PrEP, risk was greatest in those prescribed 12+ months ago (11 HIV acquisitions among 3824 person-years) (aIRR 8.13, 95% CI 2.58-25.64).

CONCLUSIONS

HIV incidence was sustained at a low level as PrEP coverage broadened among GBMSM, but did not reduce further. Efforts to support persistence and re-engagement with PrEP are warranted in those at ongoing risk of HIV.