By Bunmi Yekini
Real-world data from a San Francisco sexual health clinic show that people taking HIV pre-exposure prophylaxis (PrEP) who also used doxycycline after sex had lower rates of some bacterial sexually transmitted infections (STIs), according to a study published in the journal Sexually Transmitted Infections.
The study analysed outcomes after the San Francisco AIDS Foundation’s Magnet clinic began offering doxycycline post-exposure prophylaxis, known as DoxyPEP, to all PrEP users in November 2022. DoxyPEP involves taking the antibiotic shortly after sex to reduce the risk of bacterial infections such as chlamydia, gonorrhea and syphilis.
Researchers reviewed records from 3,081 patients who received PrEP at the clinic between June 2022 and September 2023 and who attended regular HIV and STI screening visits.
About 39% of PrEP users took up DoxyPEP. Most of those who started it were cisgender men, and the majority were between the ages of 30 and 49, the researchers said.
Before the policy was introduced, people who later chose DoxyPEP had higher rates of STIs than those who did not. After DoxyPEP became available, however, STI incidence among users fell significantly compared with the pre-intervention period.
The analysis found marked reductions in chlamydia and early syphilis among DoxyPEP users, while no statistically significant decline was seen for gonorrhea. Overall, the quarterly rate of new STI diagnoses dropped sharply after the policy took effect.
In contrast, STI rates remained largely unchanged among people who did not start DoxyPEP, the researchers reported. By the final point of the study, STI incidence was similar between users and non-users.
“We found STI incidence declined rapidly among DoxyPEP users after real-world clinical implementation,” the authors wrote, adding that continued monitoring would be needed as the approach is expanded.
The researchers cautioned that the study was based on a single clinic, used a retrospective design and had a relatively short follow-up period, which may limit how broadly the findings can be applied. They also stressed the importance of tracking long-term use, adherence and the potential impact on antibiotic resistance.
Public health experts are increasingly studying DoxyPEP as a possible new tool to help curb rising rates of bacterial STIs, particularly among populations already using PrEP for HIV prevention.