Taking doxycycline after sex can prevent STIs, another study finds
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A second study has shown that taking a single dose of doxycycline within 3 days of having condomless sex can prevent sexually transmitted infections.
The study was conducted in San Francisco and Seattle among transgender women and men who have sex with men (MSM) — two populations disproportionately impacted by the ongoing STI epidemic — who were either HIV positive or taking pre-exposure prophylaxis (PrEP) for HIV prevention.
In response, the CDC said it would collaborate with researchers in the coming months to develop interim clinical guidance on using doxycycline as post-exposure prophylaxis (PEP) for STIs and to outline additional research questions.
It will be important, for example, to determine whether on-demand doxycycline could promote resistance in STIs — especially gonorrhea — or common bacteria found on the body, such as Staphylococcus aureus, or have a negative impact on the gut, said Annie Luetkemeyer, MD, professor of medicine at the University of California, San Francisco.
Prior evidence from MSM who were being followed as part of another study on HIV PrEP and PEP demonstrated that taking doxycycline within 3 days of condomless sex halved their incidence of STIs. The impact was even larger in the new study, which showed a more than 60% reduction in STI risk per quarter among people who took the antibiotic, according to data presented by Luetkemeyer at the International AIDS Conference.
“We now have two studies that support the use of doxycycline as PEP in men who have sex with men,” Luetkemeyer said during a press briefing. “I really think we’re at a place where we need to think very strongly about rolling this out and how to incorporate this into guidelines” — not for everyone, she said, but specifically for populations that have been heavily impacted by the STI epidemic.
That appears likely. The CDC quickly published a response, saying it was “encouraged by the initial data” and would pursue guidelines.
“It will be critical to provide guidance that will maximize effectiveness for STI prevention, while minimizing both individual and potential public health risks,” the CDC said. “We must move quickly to implement powerful STI prevention strategies. And it is our public health imperative to develop responsible guidance, based on a careful consideration of all available data and public health risks and benefits — we cannot take short cuts when it comes to people’s health.”
In the randomized open-label study, Luetkemeyer and colleagues enrolled more than 500 people at HIV and sexual health clinics in San Francisco and Seattle and randomly assigned them in a 2:1 ratio to either 200 mg of doxycycline within 72 hours of condomless sex or no doxycycline.
“They can take it as often as every day depending on how much sexual contact they are having,” Luetkemeyer explained.
Participants had to be male sex at birth, living with HIV or taking PrEP and have a history of a bacterial STI and condomless sex with a male partner in the past year. The primary outcome was one or more bacterial STIs occurring each quarter.
The study was stopped early in May of this year after a planned interim analysis showed a substantially lower incidence of STIs among participants in the treatment arm.
According to an intent-to-treat analysis of patients with at least one quarter of follow-up, among 327 participants who were taking PrEP, 32% in the control arm developed a new STI compared with 11% in the treatment arm, a 66% reduction per quarter, Luetkemeyer reported. Among the 174 participants with HIV, new STIs occurred in 30.5% in the control arm and 12% in the doxycycline arm, for a reduction of 62% per quarter.
Luetkemeyer said participants in the treatment arm reported taking doxycycline 87% of the time after condomless sex. Around half took fewer than 10 doses per month, 30% took 10 to 20 doses and 16% took more than 20 doses per month. There were no serious adverse events reported, and most participants found the treatment “acceptable” or “very acceptable,” she said.
Available culture data from people with gonorrhea during the study showed a 20% rate of tetracycline resistance, which Luetkemeyer explained is a proxy for doxycycline resistance. She called this “relatively low” but said larger studies are needed to understand if using doxycycline as PEP could drive tetracycline resistance.
“We don’t really think this is going to be an issue in chlamydia and syphilis. We’re looking carefully at gonorrhea, but ... it’s going to be challenging to have definitive data from our own study because it’s a short period of follow-up,” Luetkemeyer said.
References:
CDC response to doxy-PEP data presented at 2022 International AIDS Conference. https://www.cdc.gov/nchhstp/newsroom/2022/Doxy-PEP-clinical-data-presented-at-2022-AIDS-Conference.html. Published July 27, 2022. Accessed July 27, 2022.
Luetkemeyer A, et al. Abstract 13231. Presented at: International AIDS Conference; July 27-Aug. 2, 2022; Montreal (hybrid meeting).
Perspective
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Paul A. Volberding, MD
PrEP has been one of the most exciting developments in our control of the global HIV epidemic. Although much needs to be done to implement this breakthrough more widely and equitably, there is no doubt PrEP will remain an essential HIV prevention tool. As effective as PrEP is in blocking HIV transmission, it remains true that by itself, PrEP does not prevent other STIs unless its use is linked with the protection of condom barriers. Also, individuals living with HIV are at higher risk for intercurrent STIs. The question of PrEP and PEP for non-HIV STIs has been raised, and this abstract provides important new data showing substantial success of PEP.
Investigators randomly assigned MSM and transgender women either on PrEP or living with HIV to receive oral doxycycline or not within 3 days of experiencing condomless sex. Testing for subsequent infection with gonorrhea, chlamydia or syphilis showed that those randomly assigned to doxycycline have a substantially reduced STI risk. These data provide a strong rationale for implementing this approach as part of other public health measures.
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Luetkemeyer A, et al. Abstract 13231. Presented at: International AIDS Conference; July 27-Aug. 2, 2022; Montreal (hybrid meeting).
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