PhD defence Thibaut Vanbaelen

Supervisors

• Prof. Dr. Chris Kenyon (ITM) 

• Dr. Eric Florence (UZA)

• Prof. Dr. Veronique Verhoeven (University of Antwerp)

Abstract

Human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP) is a very effective biomedical intervention to reduce HIV incidence and improve sexual health. PrEP has become a crucial component of HIV prevention, and its uptake is increasing globally, including in Belgium. However, PrEP coverage remains insufficient, and both PrEP care and users face numerous challenges. In this thesis, we describe some of these challenges, and potential interventions to address them.

First, we discuss the PrEP (care) discontinuation and ongoing HIV risk when discontinuing PrEP care. Factors contributing to discontinuation are multiple, include being in a monogamous relationship, reduced sexual activity, consistent condom use, and barriers to PrEP care (e.g., difficult access to the clinic). To address these barriers, we emphasize the importance of a differentiated, client-centered and low-threshold approach in PrEP delivery, as recommended by the World Health Organization. Moreover, it is crucial to consider the individual risk for HIV to assess the effectiveness of PrEP programs, beyond traditional retention in care metrics.

Subsequently, we explore two components of a syndemic affecting PrEP users: chemsex and non-consensual sex. Chemsex, the use of drugs during sexual encounters, can present risks and negative effects. We found that a substantial proportion of PrEP users in Belgium engaged in chemsex and expressed a willingness to reduce related risks through online applications and face-to-face counseling with healthcare providers. Non-consensual sex is another significant concern, with a considerable proportion of PrEP users reporting such experiences. However, seeking help after non-consensual sex incidents remains low, indicating a need for improved support services. PrEP clinics could play a vital role in addressing this syndemic, given that PrEP users are already familiar and engaged in care with these services.

Finally, we explored the emergence of antimicrobial resistance (AMR) in bacterial sexually transmitted infections (STIs), particularly Neisseria gonorrhoeae. AMR has been increasing in Neisseria gonorrhoeae following decades of antimicrobial exposure. Reducing antimicrobial consumption is crucial to slow down the emergence of AMR.  Our findings suggest that reducing screening intensity for Neisseria gonorrhoeae and Chlamydia trachomatis in PrEP cohorts can significantly decrease antimicrobial consumption. We also recommend using mono-therapy with ceftriaxone instead of dual-therapy with ceftriaxone and azithromycin for the treatment of Neisseria gonorrhoeae. Finally, we caution against the widespread use of doxycycline prophylaxis for STIs due to the risk of inducing AMR.

In conclusion, we recognize the positive impact of PrEP on reducing HIV incidence and improving sexual health. However, challenges in PrEP care, including coverage and discontinuation, must be addressed. The syndemic of chemsex and non-consensual sex require attention and support services within PrEP clinics. Additionally, the emergence of AMR in bacterial STIs necessitates interventions to reduce antimicrobial consumption. Our research provides insights into these areas and contributes to a better understanding of optimizing PrEP programs and addressing associated challenges.