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DoxyPrEP Cuts STI Rate in FSW Without Fueling Other Infections
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AIDS 2024, July 22-26, 2024, Munich
Mark Mascolini
Daily doxycycline preexposure prophylaxis (DoxyPrEP) cut incidence of new sexually transmitted infections (STIs) by two thirds in a small retrospective study of female sex workers (FSW) in Tokyo [1]. Daily DoxyPrEP did not affect vaginal bacterial flora in a way that promoted bacterial vaginosis or vulvovaginal candidiasis.
Doxycycline postexposure prophylaxis (DoxyPEP) significantly lowers STI rates in some well-studied risk groups, like men who have sex with men (MSM) and transgender women (TGW) [2]. In the United States, the CDC recommends DoxyPEP for MSM and TGW who had a bacterial STI in the past 12 months, if they can take DoxyPEP within 72 hours of oral, vaginal, or anal sex [2].
But Seitaro Abe and coworkers at Japan’s National Center for Global Health and Medicine noted that much less is known about doxycycline PEP or PrEP in FSW.
Abe and colleagues conducted this retrospective analysis of cisgender FSW who started DoxyPrEP to prevent STIs between October 2022 and November 2023. Their electronic medical records at a private STI clinic provided demographic data and HIV PrEP status. Women got tested every 1 to 3 months for chlamydia, gonorrhea, syphilis, bacterial vaginosis, and vulvovaginal candidiasis.
The study group included 40 cisgender FSW prescribed 100 mg of DoxyPrEP daily who had STI data available before and after starting DoxyPrEP. The researchers had vaginal smear test data for 29 women and follow-up interviews for 22 women. These women had a median age of 29 years, and all 40 were Asian. Thirty-three women (82.5%) used HIV PrEP, and 35 (87.5%) took an oral contraceptive. The most prevalent STIs at the first clinic visit were bacterial vaginosis (8 cases), chlamydia (7 cases), and gonorrhea (6 cases).
Overall STI incidence plunged from 232.3 cases per 100 person-years before women started DoxyPrEP to 79.2 per 100 person-years with DoxyPrEP, a significant two thirds fall in incidence (incidence rate ratio [IRR] 0.33, 95% confidence interval [CI] 0.13 to 0.84, P = 0.020). Most of this drop can be attributed to a nearly significant swoon in chlamydia incidence from 159.2 to 57.2 cases per 100 person-years (IRR 0.35, 95% CI 0.12 to 1.03, P = 0.056). Number of syphilis cases fell from 8 before DoxyPrEP to 0 after PrEP began. The researchers saw no significant shift in incidence of gonorrhea, bacterial vaginosis, or vulvovaginal candidiasis.
Incidence estimates per number of tests before and after starting DoxyPrEP were 10.2% and 2.6% for overall STIs, 20.7% and 5.7% for chlamydia, 7.5% and 2.2% for gonorrhea, 2.3% and 0.0% for syphilis, 17.1% and 17.0% for bacterial vaginosis and 8.5% and 8.9% for vulvovaginal candidiasis.
According to follow-up interview summaries in the medical records of 22 study participants, 16 (72.7%) claimed they missed no DoxyPrEP doses, while 6 (27.3%) said they missed 1 or 2 doses per month and no one reported missing 3 or more doses. Five women (22.7%) had nausea and vomiting when taking doxycycline daily. Twenty-one of these 22 women reported no change in condom use when on DoxyPrEP. Sixteen women (72.7%) reported less anxiety about STIs during PrEP.
The investigators noted that their study is limited by its small size, brevity, focus on PrEP instead of PEP, and lack of resistance data. Yet despite greater STI testing frequency during DoxyPrEP, STI rates fell markedly, a change suggesting DoxyPrEP can prevent STIs in FSW.
References
1. Abe S, et al. Doxycycline PrEP prevents STIs without affecting vaginal bacterial flora in female sex workers. AIDS 2024, July 22-26, 2024, Munich. Abstract OAC0803.
2. Bachmann LH, Barbee LA, Chan P, et al. CDC Clinical guidelines on the use of doxycycline postexposure prophylaxis for bacterial sexually transmitted infection prevention, United States, 2024. Recommendations and Reports. June 6, 2024. 2024;73:1-8. https://www.cdc.gov/mmwr/volumes/73/rr/rr7302a1.htm
3. Stewart J, Oware K, Donnell D, et al. Doxycycline prophylaxis to prevent sexually transmitted infections in women. N Engl J Med. 2023;389:2331-2340. doi: 10.1056/NEJMoa2304007. https://pubmed.ncbi.nlm.nih.gov/38118022/
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