Objectives We aimed to assess the awareness, willingness to use, and actual use of doxycycline post-exposure prophylaxis (doxyPEP) among men who have sex with men (MSM) and transgender women (TGW) in Belgium. Additionally, we aimed to identify factors associated with doxyPEP use and concerns regarding antimicrobial resistance (AMR).

Methods Cross-sectional online survey among MSM and TGW in Belgium in April 2024. Participants were recruited through sexual networking applications and social media of community-based organizations. Numerical variables were compared with Wilcoxon rank-sum test and categorical variables with chi-square or Fisher’s exact tests. Factors associated with doxyPEP use were assessed using logistic regression. Willingness to use doxyPEP and concerns about side-effects/AMR were assessed before and after presenting a brief paragraph on the potential effects of doxyPEP on AMR.

Results A total of 875 individuals initiated the survey. Almost all identified as men (860/875, 98.3%) with a median age of 40 years (IQR 32-48). Among all respondents, 40.4% (n=352/875) had heard of doxyPEP and 9.4% (n=82/875) had used it, among whom the majority used it within the last six months (70/81, 86.4%). In multivariable logistic regression, doxyPEP use was associated with having had ≥1 STI in the past 12 months and engagement in chemsex.

About 80% of the participants initially reported being willing to use doxyPEP, and about 50% reported being concerned about side effects. After reading about the potential effects of doxyPEP on AMR, willingness to use doxyPEP decreased to 60% and concerns of side-effects including AMR increased to around 70%.

Conclusions Approximately one in ten MSM and TGW in Belgium reported using doxyPEP, with those at highest STI risk reporting higher usage. Importantly, concerns about AMR and side effect influenced willingness to use doxyPEP. If doxyPEP is introduced, informing patients about doxyPEP benefits and risks is crucial to enable informed decision-making.

What is already known on this topic Several RCTs have shown the efficacy of doxycycline post-exposure prophylaxis (doxyPEP) on the incidence of chlamydia, syphilis, and in some instances gonorrhoea, among men who have sex with men (MSM) and transgender women (TGW). However, the potential for antimicrobial resistance (AMR) due to increased doxycycline consumption is a major concern, leading to some guidelines not recommending doxyPEP. Informal use of doxyPEP has been reported by up to 10% of MSM in countries where it is not recommended.

What this study adds We found that about one in ten MSM in Belgium has ever used doxyPEP, with a majority having used it in the past six months. DoxyPEP use was associated with higher odds of having had one or more STIs in the preceding year and having engaged in chemsex in the past six months. The willingness to use doxyPEP was high but decreased after presenting information about the potential effects of doxyPEP on AMR. In contrast, concerns regarding doxyPEP side-effects were high and further increased after presenting information about the potential effects of doxyPEP on AMR.

How this study might affect research, practice or policy By highlighting the prevalence and factors associated with informal doxyPEP use, this study can inform future research directions, guiding further investigations into patterns of STI prevention among MSM and TGW in Belgium. The insights the study adds of the impact of AMR concerns on the willingness to use doxyPEP, can influence clinical practice by emphasizing the importance of comprehensive patient education to ensure informed decision-making regarding STI prevention strategies. From a policy perspective, the study underscores the need for a comprehensive assessment of the challenges and benefits of doxyPEP, balancing its potential for reducing STI incidence with the risks of promoting antimicrobial resistance.

This study was funded by a research grant from Viatris.

This study was funded by a research grant from Viatris. Viatris played no role in the study design, collection or interpretation of the study results.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Institutional Review Board of the Institute of Tropical Medicine gave ethical approval for this work.

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All data produced in the present study are available upon reasonable request to the authors.