Just one dose of the antibiotic doxycycline taken after intercourse halved the variety of chlamydia and syphilis circumstances in San Francisco, promising new analysis reveals.

In the research, homosexual and bisexual males and transgender ladies who had a historical past of sexually transmitted infections or a number of intercourse companions got a provide of the antibiotic and requested to take two 100-milligram drugs inside 72 hours of unprotected intercourse. The technique is called doxy-PEP.

What occurred?

In results introduced Monday on the Conference on Retroviruses and Opportunistic Infections in Denver, new circumstances of chlamydia and early syphilis—however not gonorrhea—dropped drastically over the course of a yr.

“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 on the San Francisco Department of Public Health, informed the New York Times. “This is what we want for STI prevention.”

Syphilis circumstances have reached their highest rate since 1950, the CDC reported in January. Left untreated, syphilis damages the guts and mind and may trigger blindness, deafness and paralysis. Meanwhile, chlamydia an infection charges plateaued nationwide in 2022, however there have been nonetheless almost 1.7 million circumstances.

“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 professional on the University of California, San Francisco, informed the Times. She was not concerned within the research.

So far, the proof helps the case for doxycycline use solely in homosexual and bisexual males and transgender ladies.

But, “the majority of STIs in the United States occur in cisgender women,” Dr. Jonathan Mermin, director of the CDC’s National Center for HIV, Viral Hepatitis, STD and TB Prevention, informed the Times.

“Studies of whether doxy-PEP works in cisgender women should be implemented as quickly as possible,” he burdened.

After releasing draft guidelines for doxy-PEP in October, the CDC plans to situation its closing suggestions within the subsequent few months, Mermin famous.

The San Francisco Department of Public Health had already begun recommending doxy-PEP for homosexual and bisexual men and transgender women a yr earlier than the company’s draft tips have been printed.

In the newest analysis, city officials tracked month-to-month charges of chlamydia, gonorrhea and early syphilis earlier than and after the introduction of doxy-PEP in November 2022. They additionally in contrast the numbers with the speed of STI infections in cisgender ladies.

Over a 13-month interval, new circumstances of chlamydia and early syphilis throughout town dropped by 50 %, in contrast with the anticipated numbers.

Unfortunately, circumstances of chlamydia in cisgender ladies steadily elevated.

“The fact that we did not see declines in STIs in other populations not recommended for doxy, specifically cis women, strengthens the conclusion that the decline in chlamydia and early syphilis cases is related to [the] doxy-PEP rollout,” mentioned researcher Madeline Sankaran, an epidemiologist on the San Francisco Department of Public Health who introduced the findings, the Times reported.

While the outcomes are promising, Mermin cautioned that they might have been skewed by the 2022 outbreak of mpox, throughout which high-risk teams curtailed their sexual activity.