What is Doxy PEP? What vaccinations are available for STIs?

Doxy PEP background

Two recent trials (DoxyPEP and ANRS DOXYVAC) studied the use of doxycycline 200mg, taken within 72 hours after sex, and the effect this had on rates of chlamydia, gonorrhoea, and syphilis infections among the study participants. Participants were men who have sex with men and transgender women, with a mix of people living with HIV and HIV negative people taking PrEP.

The studies found that taking doxy PEP significantly reduced the bacterial STIs chlamydia, gonorrhoea, and syphilis.

During the course of the studies only a small effect on antimicrobial resistance (AMR) was recorded. Although larger-scale studies are required to get a better understanding of this.

The British Association of Sexual Health and HIV (BASHH) issued clinical guidance for doxy PEP in June 2025. Doxy PEP is likely to be available on the NHS soon.

Who might benefit from taking doxy PEP?

Gay, bisexual, and other men who have sex with men, trans women, and non-binary people having sex within those networks might benefit from taking doxy PEP if they have recently had an STI or experience recurrent STIs.

These studies did not include trans men, or other people assigned female at birth. However, it is likely that trans men, trans masculine, and non-binary people would also benefit from using doxy PEP if they have sex within these sexual networks.

The dPEP Kenya trial looked at doxy PEP in cisgender women who were already using HIV PrEP. The study found no significant reduction in STIs. This was likely due to low adherence.

While there have been no studies focusing on cisgender men who have sex with cisgender women, doxy PEP might offer some benefit for individuals who experience recurrent STIs.

Doxy PEP should not be used during pregnancy.

How to take doxy PEP

Take 200mg of doxycycline (1 x 200mg pill, or 2 x 100mg pills) within 72 hours after sex. (either doxycycline hyclate or doxycycline monohydrate).

Take no more than 200mg within a 24 hour period.

Can be taken every 24 hours if required.

Try to avoid taking doxycycline with calcium containing supplements, antacids, multivitamins, or calcium rich foods including dairy products within 2 hours, as this may reduce the drug’s effectiveness.

Doxycycline works best with an empty stomach (1 hour before or 2 hours after meals). If taking on an empty stomach causes stomach upset, it can be taken with food.

What else should I know about doxycycline?

Doxycycline is a commonly-used antibiotic and is safe and well tolerated. It has been used for long term prophylaxis for malaria. Most people don’t experience any side effects but users should be aware of potential sun sensitivity and should wear sunscreen and try to avoid prolonged periods in the sun while using doxycycline.

For more information and FAQs visit Queer Health: Doxy PEP

Where to buy doxy PEP

Generic doxycycline can be bought online from overseas sellers, the same way many people buy their own generic HIV PrEP pills.

Green Cross Pharmacy – 30 x 100mg doxycycline tablets for £4 plus £10 delivery

All Day Chemist – 30 x 100mg doxycycline tablets for £7 plus £16 delivery

Inhouse Pharmacy – 100 x 100mg doxycycline tablets for £35 plus free delivery

Vaccinations for STIs

Vaccinations against hepatitis A, hepatitis B, HPV, and mpox (monkeypox) are available for free from sexual health clinics for those who are eligible.

MenB (a vaccine for gonorrhoea) will be available on the NHS in England, Scotland and Wales from August 2025.

PrEPster has created an information sheet on hepatitis A, hepatitis B, and HPV vaccinations. Queer Health has detailed information on MenB and mpox vaccines. These resources are made available by the team at The Love Tank.