Background:
Doxycycline as bacterial sexually transmitted (STI) post-exposure prophylaxis (DPEP) has shown high prevention efficacy in clinical trials. We evaluated the uptake and impact of DPEP on Chlamydia (CT), Gonorrhea (GC), and Syphilis incidence among PrEP users in a sexual health clinic in San Francisco.
Methods:
DPEP was offered to all active PrEP clients at their clinical visits starting on 11/30/22. We included PrEP clients with at least one STI test who received DPEP for at least 30 days (DPEP users), or never initiated DPEP (non-DPEP users). The ‘pre-DPEP’ period was defined as 6/1/22-11/30/22; and the ‘post-DPEP’ period started after DPEP initiation for DPEP users. STI testing included GC and CT (urine, rectal, and pharyngeal), and syphilis. Adjusted STI incidence rate ratios (IRR) per quarter for the pre- and post-DPEP periods were evaluated, and a controlled interrupted time series (CITS) analysis with mixed-effects Poisson regression used to evaluate intervention effects.
Results:
Of the 3,081 active PrEP clients, 1,209 (39%) received DPEP during the study period. Those who received DPEP were racially/ethnically diverse with 33% White, 26% Latinx, 16% Asian, and 4% Black; and the majority were cisgender men (90%), gay (91%), and 30-49 years (62%). The demographics of non-DPEP users were similar to DPEP users. Among DPEP users, any STI incidence declined from 18.1% in the first quarter of the study period to 7.5% in the last quarter. Among non-DPEP users, any STI incidence was stable between the first and last quarter: 7.0% and 6.5%, respectively. In the pre- post-DPEP analysis, DPEP was associated with decreased STI incidence for any STI [IRR: 0.42, 95% Confidence Interval (95% CI): 0.24-0.74; p=0.003], CT (IRR: 0.33, 95% CI: 0.23-0.46; p<0.001), and syphilis (IRR: 0.22, 95% CI: 0.07-0.54; p=0.001); but not GC (IRR: 0.89, 95% CI: 0.69-1.15; p=0.383). In the CITS analysis DPEP was associated with a significant decline in the slope for any STI incidence among PrEP clients (IRR: 0.67, 95% CI: 0.46-0.96; p=0.03) (Figure 1). This decline was also significant for CT (p=0.021) and GC (p=0.003), but not syphilis (p=0.360).
Conclusions:
DPEP uptake was high reflecting strong demand when offered as part of routine PrEP care. Overall STI incidence declined rapidly after implementation demonstrating high impact of this intervention in a real-world setting. Continued evaluation of uptake, adherence, and impact on bacterial STIs will be essential as DPEP implementation expands.
