Can pre or post-exposure antibiotics prevent STIs?

While 30 years ago condoms were the mainstay in the fight against STI and HIV, their popularity is waning lately. One of the explanations is the success in the treatment of HIV; nowadays, people living with HIV can live a full life.

Men who have sex with men (MSM) and transgender people are key populations more likely to have sexually transmitted infections (STI). The HIV incidence is decreasing because of prevention strategies, such as treatment-as-prevention (TasP) and pre-exposure prophylaxis (PrEP), but the incidence of bacterial STIs (syphilis, gonorrhea and chlamydia) is increasing. STIs can cause serious complications, facilitate HIV transmission, and their treatment can cause antimicrobial resistance (AMR). Therefore, new STIs prevention strategies are needed. Two recent studies showed that doxycycline once after condomless sex (doxy-PEP) significantly reduces the incidence of bacterial STIs. This can potentially result in less antibiotic use in the long run.

Although doxy-PEP can possibly lead to STI reduction in key populations, at the same time it can lead to tetracycline AMR, dysbiosis, and increased STI transmission through behavioral change. Doxy-PEP is already used informally and is gaininig popularity among MSM across Europe. Thus, we urgently need more data on its effectiveness, side effects, STI transmission and behavioral changes. For the longer run, doxyPEP is likely not the answer since it counteracts antibiotic stewardship measures. We therefore need safer and more effective biomedical interventions that do not cause AMR to curb the ever-rising bacterial STI pandemic.