A single dose of a widely used antibiotic taken after sex can reduce the incidences of Syphilis and Chlamydia. According to reports, doxycycline has halved the incidence of chlamydia and early syphilis among gay and bisexual men and transgender women in San Francisco, city health officials announced on Monday, as reported by The New York Times.
The strategy is called doxy-PEP, shorthand for doxycycline post-exposure prophylaxis. This promising new study offers a glimmer of hope amid a rising tide of sexually transmitted infections across the United States.
As a part of the study, gay and bisexual men and transgender women who had a history of sexually transmitted infections or multiple sex partners were given a supply of the antibiotic and asked to take two 100-milligram pills within 72 hours of unprotected sex.
The results of the promising study were presented at Conference on Retroviruses and Opportunistic Infections in Denver, new cases of chlamydia and early syphilis—but not gonorrhea—dropped drastically over the course of a year.
“It’s not subtle, it is very fast and we’re seeing the beginning of it, not the end,” researcher Dr. Hyman Scott, a medical director at the San Francisco Department of Public Health, told the New York Times. “This is what we want for STI prevention.”
In January this year, the Centers for Disease Control and Prevention (CDC) reported that Syphilis cases have reached their highest rate since 1950.
If left untreated, syphilis can damage the heart and brain and can cause blindness, deafness and paralysis. Meanwhile, chlamydia infection rates plateaued across the US in 2022, but there were still nearly 1.7 million cases.
These data are simply looking at numbers of STI cases at different time points, but make me feel hopeful that doxy-PEP may be able to reduce STIs at a population level,” Dr. Ina Park, an STI expert at the University of California, San Francisco, told the Times. She was not involved in the study.
After releasing draft guidelines for doxy-PEP in October, the CDC plans to issue its final recommendations in the next few months, as per the New York Times report. Meanwhile, the San Francisco Department of Public Health had already begun recommending doxy-PEP for gay and bisexual men and transgender women a year before the agency’s draft guidelines were published.
According to media reports, the city officials tracked monthly rates of chlamydia, gonorrhea, and early syphilis before and after the introduction of doxy-PEP in November 2022. The officials also compared the numbers with the rate of STI infections in cisgender women.
Over a 13-month period, new cases of chlamydia and early syphilis across the city dropped by 50 percent, compared with the expected numbers. Unfortunately, cases of chlamydia in cisgender women steadily increased.