Is DoxyPEP working? What Australia’s 2025 data shows

DoxyPEP — a single dose of the antibiotic doxycycline taken after condomless sex to reduce the risk of some bacterial STIs — has been used in Australia since an ASHM consensus statement supported it in 2023. Three years on, Australia’s 2025 surveillance data offers the first real-world read on whether it’s making a difference. The short answer: yes for syphilis and chlamydia, much less so for gonorrhoea.

What the 2025 data shows

Data from a national network of sexual health clinics (known as ACCESS) shows that over the past three years, infectious syphilis diagnoses fell by 30% in HIV-negative and 37% in HIV-positive gay and bisexual men. Chlamydia diagnoses fell by 31% and 26% in the same two groups. Gonorrhoea diagnoses, by contrast, stayed relatively stable.

Researchers, including the Kirby Institute’s HIV epidemiology lead, have described the drop in syphilis and chlamydia as encouraging and consistent with the increasing use of doxy-PEP since 2023. It’s an association rather than proof of cause — behaviour, testing patterns and other prevention all play a part — but the pattern lines up with what doxy-PEP is expected to do.

Why gonorrhoea is the exception

DoxyPEP works well against syphilis and chlamydia, but far less reliably against gonorrhoea, because a large share of gonorrhoea in Australia is already resistant to doxycycline. That’s why gonorrhoea rates haven’t followed syphilis and chlamydia down. It’s an important caveat: doxy-PEP is not a shield against every STI, and condoms plus regular testing remain the mainstay for preventing and catching gonorrhoea early. Overuse of doxycycline also carries a broader antibiotic-resistance concern, which is one reason it’s prescribed selectively rather than to everyone.

What DoxyPEP actually is

DoxyPEP (post-exposure prophylaxis) is a single 200 mg dose of doxycycline taken as soon as possible — and within 72 hours — after condomless sex, to lower the risk of syphilis, chlamydia and, to a lesser extent, gonorrhoea. It is not the same as HIV PrEP, and it does not protect against HIV. For the full explainer, see what is DoxyPEP, or our DoxyPEP service page for how it works at Clinic365.

Is DoxyPEP right for me?

DoxyPEP is most useful for gay and bisexual men and some other people at higher risk of bacterial STIs, particularly those who have had syphilis or chlamydia before. It is prescription-only in Australia, so whether it suits you is a conversation with a doctor — weighing your individual risk against the resistance considerations above. It works best as one part of a wider approach: condoms where you want them, HIV PrEP if that applies to you, and regular STI testing.

Keep testing either way

Whether or not you use doxy-PEP, regular testing remains the single most effective thing you can do — it catches the infections doxy-PEP doesn’t prevent (gonorrhoea included) and anything picked up despite it. A full screen covers chlamydia, gonorrhoea, syphilis, HIV and hepatitis B, and most results come back within a few days.

Frequently asked questions

Does DoxyPEP actually work?

For syphilis and chlamydia, yes. Australian data shows both fell by roughly 26–37% among gay and bisexual men over three years, a decline linked to rising doxy-PEP use. It works far less reliably against gonorrhoea.

Does DoxyPEP prevent gonorrhoea?

Not reliably. Much of Australia’s gonorrhoea is already resistant to doxycycline, and gonorrhoea rates have not fallen the way syphilis and chlamydia have. Keep using condoms and testing regularly.

Who is DoxyPEP for?

Mainly gay and bisexual men and some others at higher risk of bacterial STIs. It’s prescription-only, so a Specialist GP can advise whether it’s right for you.

Is DoxyPEP a replacement for condoms or STI testing?

No. It lowers the risk of some STIs but not all, it doesn’t prevent HIV (that’s PrEP), and regular testing is still essential.