SAN FRANCISCO, CA – A San Francisco Department of Public Health (SFDPH) analysis has demonstrated that the number of chlamydia and early syphilis infections in San Francisco among men who have sex with men (MSM) and transgender women declined sharply after the Department released guidelines for the use of doxycycline post-exposure prophylaxis (doxy-PEP), an antibiotic taken after sex. The findings were presented at the Conference on Retroviruses and Opportunistic Infections today in Denver, Colorado.
The analysis of sexually transmitted infection (STI) surveillance data used modeling to predict expected trends in STI cases. It found that as of November 2023, 13-months after SFDPH’s first in the nation doxy-PEP guidance was issued, monthly reported chlamydia and early syphilis infections among MSM and transgender women decreased by 50% and 51% respectively, compared to modeled projections. Today’s findings are the first to measure the effect of doxy-PEP at the population level. SFDPH partnered with the Getting to Zero, San Francisco consortium on this analysis.
“This effort is a tremendous example of the rapid translation of research into public health practice, and shows that this promising prevention tool has the impact to help turn the curve on the epidemic of STIs that we have been facing in San Francisco and across the nation,” said Dr. Grant Colfax, Director of Health. “San Francisco continues to be at the forefront of innovation, as well as a model when it comes to protecting the sexual health of populations traditionally affected by STIs”.
While the results were promising regarding chlamydia and early syphilis, there was no decline in gonorrhea infections among MSM and transgender woman. In addition, the authors note that population-level trends in STIs are complex and can be impacted by multiple factors, including behavioral changes (such as following the 2022 mpox outbreak), and disruptions in STI testing during the COVID-19 pandemic.
“We are pleased to see these promising results. STIs are preventable, and having another tool to protect the sexual health of San Franciscans is a huge step forward," said Stephanie Cohen, Director of SFDPH’s HIV/STI Prevention in the Disease Prevention and Control Branch. “We will continue to carefully monitor citywide trends in STIs to confirm that these early promising findings result in sustained declines, and to better understand additional factors contributing to STI rates.”
San Francisco’s Early Implementation of Doxy-PEP
SFDPH became the first health department in the nation to release doxy-PEP guidelines following a clinical trial , which found that doxy-PEP reduced the chance of acquiring syphilis, gonorrhea, and chlamydia by about two-thirds if taken after sex.
In San Francisco, doxy-PEP is recommended for cis men and trans women who have had a bacterial STI in the past year and who have had condomless anal or oral sexual contact with at least one cis male or trans female partner in the past year. The guidance also recommends that a broader group be offered doxy-PEP, including cis men, trans men and trans women who report having multiple cis male or trans female sex partners in the prior year, even if they have not previously been diagnosed with an STI.
Two 100 mg pills of doxycycline should be taken ideally within 24 hours, but no later than 72 hours after condomless sex. As of December 2023, over 3,500 people in San Francisco have been prescribed doxy-PEP.
“San Francisco has long been a center of innovation, and our early implementation of doxy-PEP is an excellent example of public health experts, researchers, and community coming together and taking the lead in addressing our most critical health issues,” said San Francisco Health Officer and Director of SFDPH’s Population Health Division Dr. Susan Philip. “The staff and patients at SFDPH’s world-class sexual health clinic, San Francisco City Clinic, played a critical role in the implementation of doxy-PEP, and the clinic will continue to protect the sexual health of the community for years to come.”
SFDPH strongly encourages that individuals speak with their medical provider about doxy-PEP. Those who do not have insurance or are having difficulty accessing care, may visit SFDPH’s San Francisco City Clinic. Visit sfcityclinic.org to learn more.