RecruitingPhase 4Drug trialGot Doxy- 'Flipping the Script' on STI PEPThis study is being done to test the effects of doxycycline on inflammation and the bacteria in the body in people with HIV and in people on HIV pre-exposure prophylaxis. This drug is approved by the Food and Drug Administration (FDA) for the treatment of bacterial infections. The study team will investigate whether the drug has additional effects on inflammation or on the bacteria that live in the body.