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Prophylactic use of antibiotics for sexually transmitted infections: awareness and use among HIV PrEP users in Belgium
  1. Thibaut Vanbaelen1,2,
  2. Thijs Reyniers2,
  3. Anke Rotsaert2,
  4. Bea Vuylsteke2,
  5. Eric Florence1,
  6. Chris Kenyon1,
  7. Irith De Baetselier1
  1. 1 Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
  2. 2 Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
  1. Correspondence to Dr Thibaut Vanbaelen, Department of Clinical Sciences, Institute of Tropical Medicine, Antwerpen, Belgium; tvanbaelen{at}

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Doxycycline prophylaxis has been shown to reduce the incidence of chlamydia and syphilis infections in various studies, but researchers are worried about increasing antimicrobial resistance (AMR).1 Although not currently recommended, STI prophylaxis has been reported in high-risk men who have sex with men, with proportions ranging from 2% to 10%.2 We assessed the awareness and use of STI prophylaxis among HIV pre-exposure prophylaxis users in Belgium in a nested cross-sectional online survey in December 2021 and January 2022. Participants were recruited through social media, HIV reference centres and social/sexual networking applications. A total of 187 participants completed the survey. The median age was 46 years (IQR 38–53). The majority were born in Belgium (161/187, 86.1%) and identified themselves as male (183/187, 97.9%). Fifty-four participants (28.9%) had ever heard of STI prophylaxis, 21 (11.3%) knew someone who used it and 6 (3.2%) reported having used STI prophylaxis themselves. Three users reported taking it only after sex and three both before and after sex. Two had used doxycycline, one azithromycin, one amoxicillin and antibiotic was unknown in two cases. Two participants reported having taken STI prophylaxis in the previous month, two in the previous 1–6 months and two >12 months ago. Two participants had obtained these antibiotics through an HIV/STI clinic, one from a sex partner and three reported using leftovers. Although the use of STI prophylaxis was limited in our sample, a substantial proportion of participants were aware of STI prophylaxis or knew persons using it, suggesting that this phenomenon may be more common than initially thought. Another concern is that some antibiotics with a high propensity to induce AMR or no efficacy in reducing the occurrence of bacterial STIs were used. Sensitisation of patients and healthcare providers is needed, as well as further research on the net benefits and risks of STI prophylaxis.

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Ethics approval

This study was approved by Institutional Review Board from the Institute of Tropical Medicine, Antwerp, Belgium (IRB 1380/20). Participants gave informed consent to participate in the study before taking part.



  • Handling editor Jonathan Ross

  • Contributors TV, IDB, AR, BV and TR contributed to the study concept and design. TV performed the data analysis. TV drafted the manuscript. All authors critically revised the manuscript and approved the final version for publication.

  • Funding This research was funded by Research Foundation—Flanders as an SBO project (S004919N).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.