The CDC is recommending a new preventative treatment for sexually transmitted infections, one that Philly physicians adopted years ago

In 2018, several Philadelphia physicians, worried about rising rates of sexually transmitted infections in the city and around the country, decided to try a new method to fight their spread: an antibiotic taken after sex that functioned like a “morning-after pill,” preventing those infections from taking hold in patients.

They had seen promising early research showing that the bacteria causing painful and potentially life-altering infections such as syphilis could be wiped out with a dose of a common antibiotic, doxycycline. Many Philadelphia doctors, including those at a city-run health center, began prescribing this course of treatment for patients following unprotected sex when patients were unsure if their partner was infected. They called the practice “doxy PEP,” short for prescribing doxycycline as a post-exposure prophylactic.

These pioneering physicians found that Philadelphia-area patients, who shared their concerns about contracting STIs, welcomed a new way to prevent infections.

“There’s not a clinic session where I don’t offer it,” said William R. Short, an assistant professor of medicine at the University of Pennsylvania who specializes in treating infectious disease. “Patients don’t like me calling them to say, ‘I hate to tell you this, but you have syphilis.’ They hear that there’s an option to prevent [these diseases], and they love it.”

Now, the Centers for Disease Control and Prevention are set to recommend that physicians across the country adopt the practice. Last week, the agency drafted a recommendation for doxy PEP’s use and is now accepting public comments on the proposal.

The CDC’s proposal looks to target certain diseases within a broad category known as sexually transmitted infections, which are passed between people through sexual contact. These include syphilis, gonorrhea, and chlamydia.

Infection rates have been rising in Philadelphia and nationally for years, said Lenore Asbel, the medical specialist for the city’s sexually transmitted infection control program. In particular, she said cases of gonorrhea in the city have increased every year since 2020. This disease can cause genital discharge and painful urination; untreated, it can lead to serious complications including infertility and infections elsewhere in the body.

Syphilis cases have been trending upward since the early 2000s. Syphilis symptoms occur in stages, beginning with a painless sore and progressing to a rash, a fever, and muscle aches, among other symptoms. In rare, untreated cases, it can lead to mental problems, paralysis, and even death.

Philadelphia briefly saw a drop in reported chlamydia cases in 2019, followed by a “steady increase” since, Asbel said. Chlamydia can also present with symptoms including genital discharge and painful urination; left untreated in women, it can cause infertility and increase the risk of an ectopic pregnancy.

The CDC now plans to recommend that physicians prescribe doxy PEP to gay, bisexual, and other men who have sex with men, and transgender women, who have been infected with at least one bacterial STI in the last year and are at risk of becoming infected again.

The CDC recommendation focused on those groups because most of the clinical studies on doxy PEP involved those populations. There’s not yet enough clinical evidence for the treatment’s efficacy in other populations, according to the CDC. The agency is also monitoring whether widespread use of doxy PEP could have a worrisome consequence: the development of antibiotic-resistant bacteria, a concern for any widely used antibiotic.

The recommendations are welcome news to physicians in Philadelphia who have been concerned about local STI rates for years. “We have very high rates among many age groups and many different demographics,” said Asbel.

The city has seen high rates of STIs among young people, men who have sex with men, and transgender women, Asbel said, but added that not everyone in those groups is at high risk.

“It has to do with behaviors that increase risk — having multiple partners and unprotected sex,” she said.

Doxy PEP is best for patients who have had sex with someone but don’t know whether they had an STI, she said. If a sexual partner is known to be infected, she urged patients to seek specific treatment after having sex with someone that they know is infected with an STI.

Penn’s Short said he hoped that the CDC’s recommendation would spur more physicians to prescribe doxy PEP.

He noted that some health-care providers are reluctant to talk to patients about sex, leading their patients to avoid raising sexual health concerns. “Then it starts this problem where it’s ignored, not talked about, but unfortunately not going away,” he said.

“We need to find something else, and hopefully this is it,” he said.