Doxy-PEP Explained: A New Tool to Prevent STIs in Gay Men

A single pill of doxycycline taken after sex can lower the risk of three common sexually transmitted infections by more than half. The method is called doxy-PEP. It stands for doxycycline post-exposure prophylaxis. Health authorities in the United States, France and the United Kingdom now recommend it for specific groups of gay and bisexual men. The Dutch Health Council is still reviewing the evidence.

Doxy-PEP is one of the biggest shifts in STI prevention in years. But it is not a vaccine, and it is not for everyone. This article explains how it works, who benefits, and what the open questions are.

What is doxy-PEP?

Doxycycline is a well-known antibiotic. Doctors have used it for decades to treat acne, Lyme disease and chlamydia. With doxy-PEP, a person takes 200 milligrams of doxycycline within 72 hours after sex without a condom. Ideally within 24 hours.

The goal is to stop bacteria from causing an infection. The method targets three STIs: chlamydia, syphilis and gonorrhoea. It does not protect against HIV, hepatitis or viral STIs like herpes and HPV.

What does the research show?

The strongest evidence comes from the DoxyPEP study, published in The New England Journal of Medicine in 2023. Researchers followed about 500 gay and bisexual men and transgender women in San Francisco and Seattle. All participants either had HIV or were using PrEP.

The results were clear. Doxy-PEP cut the risk of:

• Chlamydia by about 70 percent
• Syphilis by about 75 percent
• Gonorrhoea by about 55 percent

A French study called ANRS DOXYVAC found similar results for chlamydia and syphilis. The effect on gonorrhoea was smaller, probably because of antibiotic resistance in some regions.

Based on these findings, the US Centers for Disease Control and Prevention (CDC) issued the first official doxy-PEP guideline in June 2024. The guideline recommends doxy-PEP for gay and bisexual men and transgender women who had a bacterial STI in the past year.

Why is this needed?

STI rates among gay and bisexual men have risen sharply in many countries. In the Netherlands, the RIVM reported a record number of syphilis and gonorrhoea diagnoses at sexual health clinics in 2023. Similar trends appear across Europe, according to the European Centre for Disease Prevention and Control (ECDC).

Condoms still work, but condom use has dropped since PrEP became widely available for HIV prevention. Many men feel safer about HIV but face more bacterial STIs. Doxy-PEP fills part of this gap.

Who should consider doxy-PEP?

Current guidelines focus on a specific group. The CDC recommends doxy-PEP for gay and bisexual men or transgender women who:

• Had at least one bacterial STI in the past 12 months
• Have sex without condoms with multiple partners
• Are already in regular contact with a sexual health clinic or HIV care

It is not recommended for women or heterosexual men. A study in Kenya found no clear benefit in cisgender women, possibly because of how the bacteria behave in the female genital tract. Researchers are still investigating this.

The method is also not advised for casual or one-off use. Doxy-PEP works best as part of a planned prevention strategy, combined with regular STI testing every three months.

What are the risks?

Doxycycline is generally well tolerated. The most common side effects are nausea, sun sensitivity and stomach upset. Serious side effects are rare.

The bigger concern is antibiotic resistance. Frequent use of antibiotics can train bacteria to survive treatment. This is a real public health risk. Studies so far show a small rise in resistant Staphylococcus aureus bacteria on the skin of doxy-PEP users. But there is no clear evidence yet of major resistance problems for the STIs themselves.

The WHO published a position paper in 2024 calling for careful monitoring. The organisation supports doxy-PEP for high-risk groups but warns against broad, unmonitored use. Dutch experts share this caution. The Soa Aids Nederland foundation states that doxy-PEP could be useful, but national guidelines are still being developed.

How does it fit with other prevention?

Doxy-PEP is one part of a larger toolkit. Other tools include:

• Condoms — still the only method that blocks HIV, bacterial STIs and unwanted pregnancy at once
• PrEP — daily or on-demand pills that prevent HIV
• Vaccination — against hepatitis A, hepatitis B, HPV and mpox
• Regular testing — every three to six months for people with multiple partners

Public health experts stress that doxy-PEP does not replace any of these. It adds an extra layer for those at highest risk. For people thinking about combining methods, talking with a doctor or sexual health clinic is the right first step. The same applies to people who want to understand mpox vaccination options.

What is the situation in the Netherlands and Europe?

The Dutch government has not yet issued a national doxy-PEP guideline. Some sexual health clinics offer it on a case-by-case basis. The Health Council is reviewing the evidence and is expected to publish advice in 2025.

In France, the High Council of Public Health recommended doxy-PEP in July 2024 for men who have sex with men with a recent STI. The UK Health Security Agency took a more cautious approach and is still studying the data. Germany follows a similar wait-and-see line.

The bottom line

Doxy-PEP is a real advance. For gay and bisexual men with repeated STIs, it can cut infections significantly. But it is not a magic bullet. It does not protect against HIV, it raises questions about antibiotic resistance, and it works best inside a broader prevention plan.

If you are wondering whether doxy-PEP is right for you, the next step is simple. Make an appointment at a sexual health clinic (GGD Centrum Seksuele Gezondheid) or talk to your HIV doctor. They can review your situation, explain the risks and decide together with you.

Science moves fast in this field. What was experimental two years ago is now standard care in some countries. Keeping informed — and getting tested regularly — remains the best protection.