CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

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. Conclusion: 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.

1148 Objective Assessment of Doxycycline PEP Use Among Cisgender Women in Kenya Jenell Stewart 1 , Kevin Oware 2 , Deborah Donnell 3 , Lauren R. Violette 4 , Josephine Odoyo 2 , Victor Omollo 2 , Felix Mogaka 2 , Matthew A. Spinelli 5 , Hideaki Okochi 5 , Monica Gandhi 5 , Elizabeth Bukusi 2 , Jared Baeten 4 , for the dPEP Kenya Study Team 1 University of Minnesota, Minneapolis, MN, USA, 2 Kenya Medical Research Institute, Kisumu, Kenya, 3 Fred Hutchinson Cancer Center, Seattle, WA, USA, 4 University of Washington, Seattle, WA, USA, 5 University of California San Francisco, San Francisco, CA, USA Background: Doxycycline postexposure prophylaxis taken following a condomless sexual exposure reduces incident bacterial STIs among men who have sex with men but not among cisgender women in initial trials. Adherence is a key component of effective biomedical interventions, and some initial trials of HIV PrEP among cisgender women reported null results due to low adherence, especially among those under 24 years old, despite having increased risk of HIV acquisition. Lack of efficacy reported in the dPEP Kenya Study were likely due to low use of doxycycline; factors associated with use have not yet been reported. Methods: We conducted an analysis of doxycycline use among all follow-up visits of a randomly selected subset (n=50; 200 person-visits) of participants assigned to doxycycline PEP (doxycycline hyclate 200mg taken within 72 hours of sex) within an open-label randomized trial among 449 women aged 18-30 years in Kisumu, Kenya. Participants returned quarterly over one year for STI testing and behavioral surveys; and provided hair samples for objective detection of doxycycline. The 1cm hair segment from the scalp, representing exposure over approximately the preceding month, was tested for doxycycline detectability (>0.020 ng/mg) using liquid chromatography-tandem mass spectrometry. Baseline and time-varying covariates potentially associated with doxycycline detection were assessed using modified Poisson regression with robust standard errors and generalized estimation equations. Results: Doxycycline was detected in 29.0% (58/200) of hair samples, 32.6% (58/178) when censoring pregnancy time off doxycycline. Age of 24 years or older, an independent income source, more than one partner, and no primary sex partner were all associated with detection of doxycycline. After adjustment, older age and not having a primary partner both remain significantly associated with exposure. Common risk factors for STI exposure, e.g., higher frequency of sex, transactional sex, or prior STI, were not associated with detection of doxycycline. Participants reporting concern about getting an STI 34.4% (22/64) or concern that primary partner had other partners 29.1% (23/79) did not exhibit an increase in doxycycline detection. Conclusion: Among young cisgender women taking HIV PrEP with a high prevalence and incidence of STIs, the use of doxycycline for STI prevention was overall low. Detection of doxycycline using objective measures was associated with older age and not having a primary sex partner. The figure, table, or graphic for this abstract has been removed. 1149 Doxycycline Postexposure Prophylaxis to Prevent Trichomonas vaginalis Among Cisgender Women Fredericka Albertina Sesay 1 , Kevin Oware 2 , Lauren R. Violette 1 , Deborah Donnell 3 , Josephine Odoyo 2 , Victor Omollo 2 , Felix Mogaka 2 , R. Scott McClelland 1 , Jennifer E. Balkus 1 , Elizabeth Bukusi 4 , Jared Baeten 1 , Jenell Stewart 5 , for the dPEP Kenya Study Team 1 University of Washington, Seattle, WA, USA, 2 Kenya Medical Research Institute, Kisumu, Kenya, 3 Fred Hutchinson Cancer Center, Seattle, WA, USA, 4 Kenya Medical Research Institute, Nairobi, Kenya, 5 Hennepin Healthcare Research Institute, Minneapolis, MN, USA 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.

Poster Abstracts

1150 Bacterial STI Trends Associated With the October 2022 Doxy-Prophylaxis Recommendation, San Francisco Andy Liu , Jiayuan Hao, Trevor A.Pickering, Jeffrey D. Klausner University of Southern California, Los Angeles, CA, USA Background: Sexually transmitted infections (STIs) have been on the rise in the United States over the past decade and disproportionately impact men who have sex with men and transgender women. The San Francisco Department of Public Health (SFDPH) issued guidance in October 2022 recommending clinicians to prescribe doxy-prophylaxis as an STI prevention strategy to cis men and trans women who report condomless sex with a cis male or trans female partner and have had a bacterial STI in the past year. We assessed the trends of male rectal chlamydia, male rectal gonorrhea, and adult male syphilis cases to explore the association between the doxy-prophylaxis policy and bacterial STI rates among males in San Francisco. Methods: We reviewed publicly available monthly STI reports on male rectal chlamydia, male rectal gonorrhea, and adult male syphilis between April 2020 and July 2023. The mean difference of the number of monthly STI cases from 12 months before vs. 8 months after the policy and 95% confidence intervals were calculated. We conducted a segmented linear regression analysis of the trends for each STI. To account for temporal trends related to COVID-19, we included two breakpoints, November 2021 (period of Omicron) and November 2022 (period of policy introduction). We compared the slopes of the fitted regression lines before and after. Two-sided P<0.05 was considered statistically significant. All statistics were performed in R version 4.3.1. Results: The mean monthly difference before vs. after the doxy-prophylaxis policy for male rectal chlamydia cases was a decrease of 24 cases per month (95% CI: -2 to 51), the difference for male rectal gonorrhea was a decrease of 32 cases per month (95% CI: 9 to 55), and the difference for adult male syphilis was a decrease of 31 cases per month (95% CI: 20 to 42). Before the policy recommendation, male rectal chlamydia cases increased by 0.7 per month (95% CI: -1.2 to 2.6) and after decreased by 9.1 per month (95% CI: -13 to -5.3) (p<0.001). Male rectal gonorrhea cases decreased by 3.7 per month before the policy and decreased by 3.7 cases per month after (p=0.994). Adult male syphilis cases decreased by 2.6 cases per month before the policy and decreased by 3.0 per month after (p=0.843). Conclusion: The SFDPH doxy-prophylaxis recommendation was associated with a significant decrease in male rectal chlamydia and continued decline in male rectal gonorrhea and syphilis. Given the ecologic nature of the study, further confirmation is needed.

CROI 2024 374