Administering the antibiotic doxycycline after sex (an approach known as doxyPEP) helped reduce the risk of bacterial sexually transmitted infections (STIs) in Northern California, according to the results of two real-world studies published this week. . Chlamydia and syphilis infection rates were significantly reduced, but gonorrhea was less affected.
“Our study suggests that doxyPEP may be reversing the seemingly unending trends in the rise of chlamydia and syphilis, but important questions remain about gonorrhea and antibiotic resistance. ,” said Julia Marcus, Ph.D., MPH, of the Harvard Pilgrim Healthcare Institute in Boston. the lead author of one of the reports told POZ.
Doxycycline post-exposure prophylaxis involves taking a single 200-milligram dose of the antibiotic within 72 hours after sex. Results from the DoxyPEP trial, first presented at the 2022 International AIDS Conference, showed lower risk of chlamydia and syphilis in gay men and transgender women, with smaller but still significant reductions in gonorrhea. . However, the dPEP Kenya trial reported the following year found that this approach did not work well for African cisgender women.
Now, newly published research shows that cities that were early adopters of doxyPEP are beginning to make a real-world difference.
San Francisco DPH Research
In October 2022, San Francisco first city Doxycycline is recommended prophylactically. city’s Latest guidance This exceeds the Centers for Disease Control and Prevention’s 2023 national doxyPEP guidelines and is effective for transgender men and non-binary people, as well as cisgender men who have sex with men and trans women, and who have recently had a sexually transmitted disease. It is also available to people who have never been infected.
Madeleine Sankaran, MPH, an epidemiologist with the San Francisco Department of Public Health, and her colleagues launched doxyPEP at three high-volume sexual health clinics: City Clinic, San Francisco General Hospital’s Ward 86, and the San Francisco AIDS Foundation’s Magnet Clinic. Conducted people analysis. They show changes in the monthly number of cases of chlamydia, gonorrhea, and early syphilis before (July 2021 to October 2022) and after (November 2022 to November 2023) the city guidelines were released. I looked into it.
This result was first reported at last year’s Conference on Retroviruses and Opportunistic Infections (CROI), and now JAMA Internal Medicineshowed that chlamydia and early syphilis, but not gonorrhea, were significantly reduced after implementation of doxyPEP.
More than 3,900 men who have sex with men and transgender women started doxyPEP at three clinics by the end of 2023. During the study period, there were 6,694 chlamydia cases, 9,603 gonorrhea cases, and 2,121 early syphilis cases in this group throughout the city. . Over 13 months, chlamydia cases decreased by 50% and primary syphilis decreased by 51% compared to predicted levels. In contrast, there was a small but statistically significant increase in gonorrhea.
“This study suggests that the release of San Francisco’s doxyPEP guidelines is associated with a decrease in the number of reported cases of chlamydia and early syphilis, but not gonorrhea.” [men who have sex with men] and transgender women in San Francisco,” the study authors concluded. “doxyPEP implementation support” [men who have sex with men] And transgender women at risk for sexually transmitted infections can have a significant impact on the national STI epidemic. ”
The researchers acknowledged that further analysis is needed to assess whether these reductions in sexually transmitted infections persist and to monitor the negative effects of doxyPEP use, including antibiotic resistance.
In discussing the study results, they said, “We cannot unequivocally exclude the possibility that these reductions were due to or influenced by other factors.” Sankaran said at CROI that changes in sexually transmitted disease screening in the wake of COVID-19 and changes in sexual behavior in response to the mpox epidemic in 2022 may have influenced the results. He said there is.
Nevertheless, after a decade of rising rates of sexually transmitted infections, the number of infections among gay men has declined sharply, and the number of infections among cisgender women (who are now eligible for prophylactic doxycycline) The fact that there was no corresponding reduction in chlamydia in the non-treated group suggests that doxyPEP is having a real impact. effect.
Kaiser Northern California Research
In the second study, JAMA Internal MedicineMarcus and his colleagues received HIV pre-exposure prophylaxis (PrEP) through Kaiser Permanente Northern California, an integrated health care system serving the San Francisco Bay Area and surrounding counties, including the cities of Oakland and San Jose. We analyzed doxyPEP usage and STI rates among people in the US. , Santa Cruz and Sacramento. Researchers used electronic health records to follow participants from their first STI test recorded after November 2020 until the end of December 2023 and compared STI rates before and after starting doxyPEP.
“Our patients enthusiastically embrace this proactive approach to reducing their risk of sexually transmitted infections,” study co-author Jonathan Volk, MD, MPH, of Kaiser Permanente San Francisco, wrote in the paper. mentioned in. news release. “Since doxyPEP became available to PrEP patients, the rate of positive STI tests has decreased dramatically and the need for treatment following an STI infection has decreased.”
From November 2022 to December 2023, a total of 11,551 people received PrEP. Of this group, 2,253 people, nearly one in five, also received doxyPEP. Most doxyPEP recipients were gay or bisexual men, and nearly half had a sexually transmitted disease in the previous year. On average, they were older and had been using PrEP longer than those who did not receive doxyPEP.
Among doxyPEP recipients, quarterly STI incidence rates decreased significantly after initiating prophylactic doxycycline use. Chlamydia decreased by 79% (9.6% to 2.0%) and syphilis decreased by 80% (1.7% to 0.3%). The 12% reduction in gonorrhea (from 10.2% to 9.0%) was less impressive, but still statistically significant. Specifically, the reduction was significant for rectal and urethral gonorrhea, but not for pharynx (throat) gonorrhea. During the same period, no change in STI incidence was observed among those who did not use doxyPEP.
“This study found that among individuals using HIV PrEP, administration of doxyPEP was associated with significant reductions in the incidence of chlamydia and syphilis, and modest reductions in the incidence of urethral and rectal gonorrhea. “These findings suggest that doxyPEP could have significant benefits in reducing population-level STI infections with broader implementation,” the study authors concluded.
“These small decreases in gonorrhea rates highlight the importance of regular STD testing for patients receiving doxyPEP and the need for new preventive strategies to prevent gonorrhea, such as vaccines currently in development. ,” Volk added.
Meaning of research
Taken together, these studies provide increasing evidence that doxyPEP, although less effective against gonorrhea, is an effective intervention in reducing chlamydia and syphilis.
in Invitation commentary In accompanying two reports, National Institute of Allergy and Infectious Diseases (NIAID) Director Gene Marazzo, MD, MPH, and Jodi Dion, MD, MPH, of the University of Alabama at Birmingham, have published research on gonorrhea and the potential for infectious diseases. He cautioned that results have been mixed. Drug resistance points to the need to closely track the development of antimicrobial resistance in doxyPEP users and to include measurements of drug resistance in all doxyPEP studies.
Although previous studies do not suggest that doxyPEP causes an increase in drug-resistant STI bacteria, the fact that resistant bacteria are increasing gonorrhea Although this is already common, it may help explain why prophylactic doxycycline is not as effective against gonorrhea as it is against chlamydia or syphilis. Among people at high risk for sexually transmitted infections, those using doxyPEP may actually use fewer antibiotics than those who receive full treatment after infection.
“These reports are part of an important scientific process that moves clinical research into large-scale implementation,” Marazzo said in the paper. NIAID News Release. “DoxyPEP has proven to be an important intervention in efforts to reduce the incidence of sexually transmitted diseases while continuing to invest in research to develop safe and effective preventive vaccines and next-generation antibiotics.” It has been.”
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