An emerging trend in STI Management: Antibiotic STI Post-Exposure Prophylaxis Prevalence and Determinants in Recent Surveys

Abstract Objectives This study aimed to estimate the prevalence of antibiotic post-exposure prophylaxis (STI PEP) use among gay, bisexual and other men who have sex with men (GBMSM) in England, and to identify demographic and behavioural factors associated with STI PEP use among early adopters. Methods We synthesised individual-level data from nine surveys conducted between 2019 and 2024. To harmonise variables that differed subtly across surveys, we generated composite indicators for STI diagnosis, chemsex, and condomless sex. Multiple imputation was used to address partial missingness; participants missing core sociodemographic data were excluded. The primary outcome was self-reported STI PEP use. We calculated the prevalence of use in each survey and assessed associations using mixed-effects logistic regression. Composite variables were included as random effects if they were found to have an interaction with survey. Results Across nine surveys with 14,142 participants, STI PEP use prevalence ranged from 3.61% (95% confidence interval (CI): 2.78–4.68%) in RiiSH 2020 to 13.05% (11.85–14.36%) in RiiSH 2024. Use was higher among those aged 40–44 (adjusted odds ratio (aOR) = 1.26; 95% CI: 1.00–1.58) and lower in those under 25 (aOR = 0.56; 0.39–0.82) or over 65 (aOR = 0.64; 0.41–0.99), compared to ages 30–34. Transgender women (aOR = 3.87; 1.75–8.50), Black (aOR = 1.85; 1.34–2.56) and Asian (aOR = 1.43; 1.09–1.88) individuals, and people living with HIV (aOR = 3.40; 2.69–4.31) had higher odds of use, compared with cisgender male, White, and HIV negative individuals, respectively. Chemsex (aOR = 2.15; 1.80–2.56), condomless sex (aOR = 1.59; 1.32–1.92), and recent STI diagnosis (aOR = 1.83; 1.34–2.51) were also associated with use. Conclusion STI PEP use was more common among those practising behaviours associated with higher STI risk. However, participation and sampling biases limit finding generalisability, particularly to underrepresented groups such as women, ethinic minorities and heterosexuals. This analysis will provide a baseline from which to estimate the impact of the recommendation of doxycycline for STI post-exposure prophylaxis in the UK.