A new study published in JAMA Internal Medicine demonstrates that using doxycycline after sexual exposure—known as doxyPEP—effectively reduces the incidence of syphilis, chlamydia, and gonorrhea in patients at Kaiser Permanente Northern California (KPNC). The method involves taking a dose of doxycycline within 72 hours of potential exposure to reduce the risk of acquiring these bacterial sexually transmitted infections (STIs).

The research, which focused on KPNC patients who also take HIV pre-exposure prophylaxis (PrEP), found that doxyPEP significantly decreased STI rates. DoxyPEP was offered to approximately 12,000 KPNC patients on PrEP, with nearly 20%, or 2,253 people, opting to use the treatment in its first year starting in November 2022. The majority of those prescribed doxyPEP were gay and bisexual men and transgender women.

The study compared STI rates before and after the prescription of doxyPEP and found a significant reduction:

• Chlamydia decreased by 79%,

• Syphilis by 80%

• Gonorrhea by 12%

Dr. Jonathan Volk, an infectious disease specialist and co-author of the study, highlighted that the adoption of doxyPEP had a profound impact, leading to fewer positive STI test results and less need for post-exposure treatment.

Although the reduction in gonorrhea cases was smaller than in earlier clinical trials, the reasons for this discrepancy remain unclear but may be linked to changes in antibiotic resistance. Dr. Volk emphasized the need for regular STI testing and further research into novel prevention strategies for gonorrhea, including the development of vaccines.

Dr. Michael Silverberg, an HIV epidemiologist with the Kaiser Permanente Division of Research, noted that their healthcare system is ideal for testing this new STI prevention method, thanks to a large patient base, ample data, and a commitment from both patients and providers to adopt effective preventive measures.

Since its introduction in 2022, doxyPEP has become a standard practice for KPNC patients on PrEP or those diagnosed with HIV who are at risk for bacterial STIs. Dr. Volk pointed out the ongoing challenges posed by rising STI rates, particularly syphilis, making it crucial to have effective preventive tools in place.

While doxyPEP has been shown to be effective primarily for individuals assigned male at birth, it has not demonstrated efficacy in young women, as indicated by a clinical trial conducted in Kenya. Research continues to explore STI prevention strategies for women.

In a related study, led by the Harvard Pilgrim Health Care Institute and involving collaboration from Kaiser Permanente Northern California, Mid-Atlantic States, and Georgia, researchers also confirmed that doxyPEP is effective in reducing chlamydia and syphilis rates in routine clinical care. This study, the largest of its kind, used pharmacy data to track doxyPEP usage among KPNC's HIV PrEP population. Nearly 20% of the 12,000 HIV PrEP users filled prescriptions for doxyPEP within its first year.

The results showed a 79% reduction in chlamydia, an 80% decline in syphilis, and a 12% decrease in gonorrhea cases. Dr. Volk noted that while the decline in gonorrhea was modest, the study's findings still underscore the importance of regular STI testing for individuals using doxyPEP.

The rising number of syphilis cases, including an increase in congenital syphilis, underscores the urgent need for preventative tools like doxyPEP. Dr. Julia Marcus, a senior author of the study, highlighted that more research is needed to explore the potential effects of doxyPEP on antimicrobial resistance. Despite this, the study suggests that expanding the use of doxyPEP could significantly help reduce STI transmission and improve sexual health overall.

References:

1. Traeger MW, Leyden WA, Volk JE, et al. Doxycycline Postexposure Prophylaxis and Bacterial Sexually Transmitted Infections Among Individuals Using HIV Preexposure Prophylaxis. JAMA Intern Med. Published online January 6, 2025. doi:10.1001/jamainternmed.2024.7186

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(Rehash/Sai Sindhuja K/MSM)