San Francisco reports significant STI decline using doxyPEP

Research indicates that taking the antibiotic doxycycline after sex can lower the risk of sexually transmitted infections (STIs). This method, known as doxyPEP, is gaining support based on findings presented at the recent Conference on Retroviruses and Opportunistic Infections in 2025. DoxyPEP involves taking a dose of doxycycline within 72 hours after sexual activity. Studies in San Francisco show that after its introduction in late 2022, there was a notable decline in chlamydia and syphilis cases—about 50% citywide. Gonorrhea rates also showed improvement, but to a lesser extent. At the San Francisco AIDS Foundation's Magnet clinic, over 2,500 people received doxyPEP prescriptions, and their STI rates were analyzed. Researchers found a significant reduction in STIs among doxyPEP users. Syphilis cases dropped by 89%, chlamydia by 81%, and gonorrhea by 44%. This suggests that doxyPEP effectively reduces STIs, especially with timely use. In a second study, researchers examined how well eligible clients adhered to doxyPEP guidelines. Of the clients who were prescribed doxyPEP, approximately 61% reported taking at least one dose. However, adherence varied among different age groups and demographics. Young people and those without stable housing were less likely to consistently follow the regimen. Despite some challenges with adherence, the overall impact of doxyPEP on reducing STIs is promising. Researchers believe that increasing awareness and access could further enhance its effectiveness. They also noted that individuals often tailor their use of doxyPEP based on the type of sexual encounters, suggesting an informed approach by many users.