Background:
Trichomonas vaginalis, the most prevalent curable sexually transmitted infection (STI), disproportionately affects cisgender women, leading to reproductive complications and increased HIV acquisition risk. In-vitro studies suggest doxycycline as a potential treatment; however, no study has explored the ability of doxycycline to prevent T. vaginalis infection.
Methods:
We conducted an open-label randomized trial among 449 women (18-30 years) taking oral HIV preexposure prophylaxis (PrEP) in Kisumu, Kenya. Participants were randomized to doxycycline postexposure prophylaxis (dPEP), 200mg within 72 hours of condomless sex, or standard of care (SOC), quarterly STI screening and treatment. All participants were followed for 12 months with quarterly visits for STI testing, including T. vaginalis testing (Cepheid GeneXpert) and data collection on various health and behavioral parameters. The trial had over 90% power to detect a 50% reduction in incident T. vaginalis infections. An intention-to-treat analysis utilizing generalized estimating equations was performed.
Results:
Baseline characteristics were similar in the dPEP (n=224) and SOC groups (n=225). Overall, participants had a median age of 24 years, reported a median of 2 sexual partners, and 36.7% engaged in transactional sex. Retention in our study was high at 97% of expected scheduled visits. There were 56 incident T. vaginalis infections: 27 in the dPEP group and 29 in the SOC group, contributed by 46 participants. There was no significant decrease in T. vaginalis incidence when comparing the dPEP group to the SOC group (RR: 0.96, 95% CI: 0.54-1.73, p=0.9). In an analysis censoring participants upon pregnancy (n=80), there was no notable decrease in incident T. vaginalis infection (RR: 1.07, 95% CI: 0.58-1.97). Subgroup analyses by age groups, hormonal contraceptive use, transactional sex, and STI detected at baseline revealed similar findings. In a subset of 50 participants assigned to dPEP, doxycycline was found in all quarterly hair samples for only 29% of participants.
Conclusions:
Randomization to the doxycycline PEP group was not associated with a decreased incidence of T. vaginalis infections among cisgender women taking oral PrEP in Kenya. Low use of doxycycline may have contributed to this null result, highlighting the need to explore its role in preventing T. vaginalis in future research.
