Impact of doxycycline postexposure prophylaxis on sexually transmitted infections within a statewide community healthcare system

OBJECTIVES: This study evaluated the impact of doxycycline postexposure prophylaxis (DoxyPEP) prescribing on sexually transmitted infection (STI) incidence proportion in an underserved population receiving care from a statewide community healthcare system. DESIGN: Retrospective cohort study was conducted using pharmacy and electronic health records data between 4 May 2021 and 1 April 2025. Primary outcome was the overall STI incidence proportion during 12 months prior to and following DoxyPEP initiation. Secondary outcomes included categorizing bacteria and site-specific STIs and exploring the association between DoxyPEP, preexposure prophylaxis (PrEP), and STI incidence proportion. METHODS: Pharmacy dispensing reports and patient demographic information were combined with EHR laboratory-confirmed STI results for review and analysis. Patient data were included if the DoxyPEP prescription was written by an Equitas Health provider and dispensed by the in-house pharmacy, and at least one documented STI test during the 12 months before and after the DoxyPEP initiation. Data were excluded if the prescription originated from an outside provider or was sold after 1 April 2025. RESULTS: Overall STI incidence proportion decreased from 30.5% preintervention to 17.6% postintervention (P < 0.001) for the 1,111 included patients. Reductions were observed in chlamydia (17.3-3.1%, P < 0.001) and syphilis (3.5-0.6%, P < 0.001), while gonorrhea incidence decreased slightly (16.9-15.2%, P = 0.24). Rectal and urine chlamydia infections experienced the largest decline, and no association was found with PrEP use. CONCLUSION: DoxyPEP use was associated with a significant reduction in overall STI incidence proportion in a high-risk population, supporting this prevention strategy.