From the BC Centre for Disease Control newsroom

A new clinical trial is set to test whether taking the antibiotic doxycycline daily or after a sexual encounter can help prevent the bacterial sexually transmitted infections (STIs) syphilis, gonorrhea and chlamydia. 

The study is co-led by Dr. Troy Grennan, medical lead for STI/HIV Services with the B.C. Centre for Disease Control (BCCDC), and involves multiple sites across the country. Recruitment has started in Vancouver, with other Canadian sites to follow, and the goal is to recruit 560 people who are likely to be exposed to STIs. 

Study participants will be randomly assigned to one of two groups, to assess whether taking the antibiotic doxycycline reduces the chances of getting an STI after having sex with someone with an infection. The first group will take doxycycline daily as a pre-exposure prophylaxis or PrEP. The second will take doxycycline only after a sexual encounter as a post-exposure prophylaxis or PEP. This is the first study globally to compare these two STI prevention approaches.

“Rates of bacterial STIs have been increasing for well over a decade. We need new tools that are effective, safe, and acceptable to the people who use them, to help reduce the risk of infection and improve sexual health,” said Dr. Ann Burchell, a co-principal investigator based at St. Michael’s Hospital, a Unity Health site in Toronto. 

“The DISCO trial will provide important new evidence on whether the PrEP and PEP approach, so effective for HIV, can also work for other STIs.”