The effect of initiating testosterone-based and estradiolbased gender-affirming hormone therapy on PrEP uptake: Evidence from whole-of-population administrative data in Australia
Melbourne Institute Working Paper No. 13/26
Date: September 2026
Author(s):
Abstract
BACKGROUND: Trans and nonbinary (‘trans’) people experience a disproportionate HIV burden but use fewer HIV prevention strategies, including pre-exposure prophylaxis (PrEP), relative to the general population. Emerging literature suggests an association between gender affirming hormone therapy (GAHT) and PrEP uptake, however the evidence is mixed and limited to cross-sectional analyses of transfeminine people on estradiol-based GAHT, with no data in transmasculine people on testosterone-based GAHT. METHODS: In this quasi-experimental study, we analysed linked, whole-of-population administrative health records (2018-2025) for 5,796 transmasculine and 8,079 transfeminine Australians who initiated testosterone-based GAHT and estradiol-based GAHT. Using a stacked event-study design, we compared changes in monthly PrEP uptake (supply of any PrEP script) in the 36 months before and 24 months after GAHT initiation with contemporaneous changes among people of a similar age who initiated the same regimen in the future. Effects were estimated separately for transfeminine and transmasculine people and compared to uptake 13 to 18 months pre-GAHT. FINDINGS: For both transfeminine and transmasculine people, PrEP uptake did not significantly vary relative to the reference period and was stable over time (<1% uptake). In the six months following GAHT initiation, PrEP uptake rose by 0.18 percentage points (95%CI: 0.07 to 0.29) among transmasculine people and 0.43 percentage points (95%CI: 0.15 to 0.70) among transfeminine people and increased steadily thereafter. Averaged over the 24 months following initiation, the probability of monthly PrEP uptake increased by 0.34 percentage points (95%CI: 0.20 to 0.48) among transmasculine people and 0.58 percentage points (95%CI: 0.31 to 0.86) among transfeminine people. INTERPRETATION: In this nationwide cohort study, GAHT initiation was associated with increased PrEP uptake among both transmasculine and transfeminine people. These findings highlight the role that access to gender-affirming care can play in HIV prevention for trans communities.