Pre-exposure prophylactic with doxycycline regimen decreases STI risk in sex workers, reveals research

A new study published in the journal of JAC-Antimicrobial Resistance showed that the pre-exposure preventive doxycycline regimen (doxyPrEP) dramatically decreased the overall incidence of sexually transmitted infections (STIs) among cisgender female sex workers (FSWs) without raising the frequency of other vaginal infections.

Syphilis, chlamydia, and gonorrhea are examples of bacterial STIs that are frequently asymptomatic but can have serious side effects, such as infertility and vertical transmission, among cisgender women, especially female sex workers. FSWs accounted for 38% of syphilis cases among Japanese women in 2021, demonstrating the substantial correlation between syphilis and sex work.

Although doxycycline has been shown to be successful in preventing bacterial STIs, its efficiency in preventing STIs in high-risk cisgender women is still unclear, underscoring the need for focused STI preventive measures in this demographic. Thus, this study examined the influence of doxycycline pre-exposure prophylaxis on vaginal flora among FSWs as well as its efficacy in avoiding STIs.

40 FSWs who were at least 18 years old and started taking 100 mg of doxyPrEP per day for STI prevention at a private clinic in Tokyo, Japan, between October 1, 2022, and November 14, 2023, were included in this retrospective analysis. Using fixed-effects Poisson regression models, the incidence rate ratios (IRR) for syphilis, bacterial vaginosis (BV), chlamydia, gonorrhea, and vulvovaginal candidiasis (VVC) were calculated. The study included follow-up clinical evaluations to assess adherence, side effects, and satisfaction.

After starting doxyPrEP, the overall STI incidence dramatically decreased from 232.3 to 79.2/100 person-years (IRR = 0.33, P = 0.020). Syphilis cases decreased to zero, while the decrease in chlamydia had marginal statistical significance (IRR = 0.35, P = 0.056). The incidence of gonorrhea, BV, and VVC did not significantly alter. High adherence to doxyPrEP, the absence of significant side events, and high satisfaction with doxyPrEP were all reported in follow-up clinical evaluations.

Overall, without raising the frequency of other vaginal infections, the pre-exposure prophylactic doxycycline regimen (doxyPrEP) dramatically decreased the overall incidence of STIs among cisgender FSWs in this trial. There were no notable side effects associated with doxycycline, and participants expressed a high level of satisfaction with doxyPrEP. 

Source:

Abe, S., Mizushima, D., Ando, N., Kawashima, A., Uemura, H., Shibata, S., Moro, H., Kikuchi, T., Gatanaga, H., Oka, S., & Shiojiri, D. (2025). Doxycycline pre-exposure prophylaxis prevents sexually transmitted infections without affecting vaginal bacterial flora in female sex workers. JAC-Antimicrobial Resistance, 7(2). https://doi.org/10.1093/jacamr/dlaf054