Preventing bacterial STIs in high-risk MSM and TGW using doxycycline and vaccination

Doxycycline PEP and 4CMenB as a Comprehensive Prevention Strategy in MSM and TGW at High Risk for Bacterial STIs Within the Swiss HIV Cohort Study

Observational University of Zurich · NCT06242730

This study is testing if giving doxycycline and a specific vaccine can help prevent bacterial STIs in high-risk men who have sex with men and transgender women.

Quick facts

Study typeObservational
Enrollment400 (estimated)
Ages18 Years and up
SexAll
SponsorUniversity of Zurich Academic / other
Locations1 site (Zurich)
Trial IDNCT06242730 on ClinicalTrials.gov

What this trial studies

This study evaluates the effectiveness of offering event-driven doxycycline post-exposure prophylaxis (PEP) and 4CMenB immunization to men who have sex with men (MSM) and transgender women (TGW) at high risk for bacterial sexually transmitted infections (STIs). Participants from the Swiss HIV Cohort Study who meet specific criteria will be offered this prevention package, and the incidence of STIs will be compared between those who accept and those who decline the intervention over a 12-month period. Additionally, the study includes sub-studies investigating the impact of doxycycline PEP on the microbiome and antibiotic resistance patterns.

Who should consider this trial

Good fit: Ideal candidates include MSM and TGW aged 18 and older who are part of the Swiss HIV Cohort Study and have a history of bacterial STIs or condomless sex.

Not a fit: Patients who are not part of the Swiss HIV Cohort Study or have contraindications to doxycycline or 4CMenB will not benefit from this study.

Why it matters

Potential benefit: If successful, this approach could significantly reduce the incidence of bacterial STIs among high-risk populations.

How similar studies have performed: Other studies have shown promise in using doxycycline for STI prevention, indicating potential success for this approach.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

≥ 18 years of age

* Participant in the SHCS
* On antiretroviral therapy with suppressed viral load for ≥ 3 months
* MSM or TGW
* ≥ 1 bacterial STI (syphilis, CT, MG, or NG) within the past 3 years and/or reporting condomless sex with ≥ 1 occasional partner within the last 6 months
* Consenting for off-label use of doxycycline as PEP and/or 4CMenB for the prevention of bacterial STIs
* No allergy or intolerance to doxycycline or 4CMenB
* No other contraindication for doxycycline (e. g. co-medication)

Exclusion Criteria:

* Not participating in the SHCS

Where this trial is running

Zurich

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Doxycycline STI PEPDocycyclinePostexposure PropylaxisBacterial sexaully tarnsmitted diseasesSexuylly transmitted diseasesPeople living with HIV
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.