Two Studies Show Doxy PEP is a Winning Strategy
Two studies published in this month’s JAMA Internal Medicine offer encouraging findings about the use of doxy PEP. One study in San Francisco found lower rates of syphilis and chlamydia after doxy PEP was introduced than would have been expected. Another study in Northern California found fewer case of chlamydia, syphilis, and gonorrhea among PrEP users who also used doxy PEP. While there’s not enough data to prove a direct causal connection yet, the authors of both studies believe that the early doxy PEP roll out in parts of California is behind decreasing STI rates in the state.
Doxy PEP is a new STI prevention strategy. Users take the antibiotic doxycycline after condomless oral or anal sex to prevent chlamydia, gonorrhea, or syphilis. Early studies showed that it can reduce the risk of syphilis and chlamydia by 80% or more. It can also reduce the risk of gonorrhea by 50% when used by men who have sex with men (MSM) and transgender women who have sex with men. Research on cisgender women who have penis-in-vagina sex has not found doxy PEP to be effective.
San Francisco was an early adopter of this strategy. One of the new studies looked at bacterial STI rates in that city after the introduction of doxy PEP. It compared those numbers to projected rates based on past data. Researchers looked at real and projected numbers over a 13-month period that ended in November 2023. They found that chlamydia was down 50% compared to projections and early syphilis was down 51%. Gonorrhea cases, however, were higher than the projected rates for that period.
The other study was conducted among Kaiser Permanente patients in Northern California. It included 11,551 people who were taking PrEP to prevent HIV. The researchers found that those who also took doxy PEP had fewer cases of all bacterial STIs. Specifically, quarterly positive tests were down by 79% for chlamydia, 80% for syphilis, and 12% for gonorrhea. In contrast, rates of these STIs remained stable among those participants who took PrEP but did not use doxy PEP.
Researchers noted that the declines in gonorrhea cases only included infections of the urethra or anus. There was no decline in cases of gonorrhea of the throat. More research is needed to understand why doxy PEP is ineffective against throat infection.
There are concerns about antibiotic resistance and whether widespread use of doxy PEP could add to the problem. The bacteria that cause gonorrhea, for example, has already shown resistance to full classes of antibiotics. In fact, existing resistance to doxycycline may be why doxy PEP is not as effective against gonorrhea. The fear is that that increasing the use of doxycycline will give bacteria more opportunity to evolve antibiotic resistance. The authors of both studies agree that this issue needs to be further investigated.
The Centers for Disease Control and Prevention (CDC) offer guidelines on doxy PEP use. CDC recommends that providers discuss doxy PEP with men who have sex with men and transgender women who have sex with men—especially those who’ve had an STI in the last year.
These new studies provide a glimpse of how use of doxy PEP among MSM and transgender women could positively impact STI rates on a population level.
More to Explore
Mpox Is Still Spreading in the U.S.
Mpox used to be rare in the United States. Before 2022, most cases were in people who’d traveled internationally or who’d had had contact with animals imported from other countries. That changed with the global mpox outbreak that began in 2022. That year, there were
Federal Government Invests $4 Million to Prevent Syphilis in Newborns
The U.S. Department of Health and Human Services (HHS) is investing $4 million to expand rapid syphilis testing. The goal is to find and treat more cases of syphilis during pregnancy to prevent congenital syphilis and its complications.
ACOG Recommends Removing Fallopian Tubes Instead of Tubal Ligation
Studies show that removing fallopian tubes can reduce a person’s lifetime risk of ovarian cancer by as much as 78%. Based on this evidence, ACOG issued new guidelines encouraging doctors to remove fallopian tubes in certain situations, including for birth control.
BV and STIs Often Happen at the Same Time
A new study adds to growing evidence that bacterial vaginosis (BV) and sexually transmitted infections (STIs) often occur together.
Doxy PEP Becoming Less Effective Against Gonorrhea
A new study found that while doxy PEP provides strong protection against chlamydia and syphilis, its ability to prevent gonorrhea has rapidly declined. Researchers believe that growing antibiotic resistance may be one reason why.
CDC Offers Guidance on Sexually Transmitted Ringworm (TMVII)
CDC is is asking clinicians across the to pay close attention to possible infections caused by sexually transmitted ringworm—TMVII.
Managing Herpes: The Science, The Facts, The Feelings
Managing Herpes: The Science, The Facts, The Feelings helps take the mystery out of herpes, explaining everything from diagnosis and treatment, to symptom management, to herpes and pregnancy.
HIV Testing
The only way to tell you have HIV is get tested. Testing is recommended at least once for everyone, and may be recommended more often for some. Testing can be quick, easy and confidential.