Research Summary

Post-Exposure Prophylaxis for STI Prevention for Individuals With HIV, On PrEP

The use of doxycycline as post-exposure prophylaxis is efficacious at reducing incident sexually transmitted infections (STIs) among men who have sex with men (MSM) as well as among transgender women (TGW) who are living with HIV or on pre-exposure prophylaxis (PrEP), according to the results of a recent study presented at International AIDS Conference 2022.

Researchers conducted a randomized, open-label trial that included 554 individuals from Seattle, WA and San Francisco, CA. All participants had N. gonorroheae (GC), C. trachomatis (CT), or early syphilis infections within the past year. Of the total participants, 360 were on PrEP, 194 had HIV, 65% were White, 8% were Black, 10% were Asian, 30% were Latinx, and 3% identified as TGW or nonbinary.

The participants were randomized to receive either doxycycline hyclate 200 mg or no medication within 72 hours of condomless sex. Participants underwent STI testing at enrollment, quarterly, and when symptomatic. In the past year, 67% of participants had GC, 58% had CT, and 20% had syphilis, whereas 18% had GC, 10% had CT, and 2% had syphilis at enrollment.

Assuming a 10% quarterly STI incidence, the trial had more than 80% power to detect a 50% reduction in STI incidence. The intent to treat analysis compared relative risk (RR) of an STI per quarter. 

The results indicated reductions were observed in GC, CT, and syphilis infections. Among the individuals on PrEP, 29.5% (n = 65) of patients had STIs in the control group and 9.6% (n = 47) had STIs in the medication group (RR = 0.33; [95% CI, 0.23 - 0.47], p < .0001). Similarly for patients with HIV, 27.8% (n = 30) and 11.7% (31%) had STIs, respectively (RR = 0.42; [95% CI, 0.25 - 0.75], p = .0014). No serious or grade 2 adverse effects were reported in relation to doxycycline.

“Doxycycline 200 mg taken within 72 hours after condomless sex significantly reduced STIs in MSM and TGW,” the researchers concluded. “Effects on antimicrobial resistance, gut microbiome, and sexual behavior are being assessed as important considerations for this STI prevention strategy.”



Luetkemeyer A, Dombrowski J, Cohen S, et al. Doxycycline post-exposure prophylaxis for STI prevention among MSM and transgender women on HIV PrEP or living with HIV: high efficacy to reduce incident STI’s in a randomized trial. Paper presented at: International AIDS Conference 2022; July 29-August 2, 2022; Montreal, Canada. Accessed January 10, 2023.