San Francisco saw a “significant decline” in sexually transmitted infections in 2025, city health officials said Monday, crediting expanded prevention efforts and the growing use of a post-exposure antibiotic.
Cases of syphilis fell 24%, chlamydia dropped 18% and gonorrhea declined 5% compared with 2024, according to the San Francisco Department of Public Health.
The data were released at the start of national Sexually Transmitted Infection Awareness Week.
The most pronounced decreases were among men who have sex with men and transgender women, groups that have historically borne a disproportionate share of infections.
Health officials pointed to increased use of doxycycline post-exposure prophylaxis, known as doxy-PEP, as a key driver. The treatment involves taking a dose of antibiotics after sex to prevent certain bacterial STIs.
“STI prevention is a key priority for SFDPH, and we are thrilled to see that doxy-PEP is making a difference in our communities,” Daniel Tsai, director of health, said in a statement.
The local data build on earlier research from San Francisco and Kaiser Permanente Northern California showing that doxy-PEP can significantly reduce rates of syphilis and chlamydia, particularly among gay and bisexual men and transgender women.
Even with the declines, public health leaders stressed that no single tool will reverse the city’s STI trends on its own.
“We are excited to see the progress being made in lowering STI diagnoses in San Francisco,” San Francisco Health Officer Dr. Susan Philip said in a statement. “We encourage the public to keep up the momentum by taking actions — such as getting tested — to protect their sexual health.”
Dr. Stephanie Cohen, director of STI and HIV prevention and control for the department, said the results reflect years of research and coordination across the city’s health system.
“The remarkable drop in STI cases in San Francisco is due in large part to the trailblazing work that made the rollout of doxy-PEP possible,” Cohen said in a statement.
Officials cautioned that sexually transmitted infections remain a persistent public health challenge nationwide, with rates rising over much of the past decade. They urged residents to continue basic prevention steps, including routine testing, vaccination and open conversations with partners and providers.
Testing and treatment are available through city clinics and other programs, including for people without insurance, the department said.