Doxycycline postexposure prophylaxis (doxyPEP) given to people who were receiving HIV preexposure prophylaxis (PrEP) were shown to reduce chlamydia by 79%, syphilis by 80%, and gonorrhea by 12%.1
The study’s results were published in JAMA Internal Medicine.
“Among doxyPEP recipients, quarterly chlamydia positivity decreased from 9.6% (95% CI, 9.0%-10.3%) before starting doxyPEP to 2.0% (95% CI, 1.5%-2.6%) after starting doxyPEP (RR, 0.21; 95% CI, 0.16-0.27; P < .001), with significant declines for each anatomic site of infection. Quarterly gonorrhea positivity decreased from 10.2% (95% CI, 9.6%-10.9%) before starting doxyPEP to 9.0% (95% CI, 8.0%-10.1%) after starting doxyPEP (RR, 0.88; 95% CI, 0.77-1.00; P = .048); site-specific declines were significant for rectal (RR, 0.81; 95% CI, 0.67-0.97; P = .02) and urethral (RR, 0.56; 95% CI, 0.40-0.79; P = .001) gonorrhea, but not pharyngeal gonorrhea,” the investigators wrote. “Quarterly syphilis positivity decreased from 1.7% (95% CI, 1.4%-1.9%) before starting doxyPEP to 0.3% (95% CI, 0.2%-0.6%) after starting doxyPEP (RR, 0.20; 95% CI, 0.11-0.37; P < .001).”
Read More: Can Daily Doxycycline Prevent STIs?
What You Need to Know
Doxycycline postexposure prophylaxis (doxyPEP) significantly reduced the incidence of chlamydia (79%) and syphilis (80%) among individuals receiving HIV PrEP. However, the reduction in gonorrhea was modest (12%), with limited protection against pharyngeal gonorrhea.
DoxyPEP recipients were predominantly male (98.9%) and older on average (40.4 years vs. 39.8 years in non-doxyPEP users). Nearly half (48.6%) had a prior STI in the year before starting doxyPEP, and they had been using HIV PrEP longer (4.2 years vs. 3.4 years).
Despite limited efficacy against gonorrhea, the study concludes that doxyPEP could offer substantial benefits in reducing STI transmission at a population level with broader implementation.
Study Specifics and Other Takeaways
This was a retrospective cohort study of adults at least 18 years of age and older who were provided with HIV PrEP at Kaiser Permanente Northern California during November 1, 2022, to December 31, 2023. Investigators reviewed electronic health data and determined which HIV PrEP users were being dispensed doxyPEP and those who were not.
Of the 11,551 HIV PrEP users, 2253 (19.5%) were dispensed doxyPEP. Within this subgroup (2228 doxyPEP users), 98.9% were male and nearly half of them (48.6%) had an STI in the year before starting doxyPEP.
In addition, doxyPEP recipients were older (40.4 years of age) vs (39.8 years of age) in the non doxyPEP group. The doxyPEP group has also been using HIV PrEP longer (4.2 years) vs (3.4 years) in the non doxyPEP group.
With only a seemingly 12% reduction for gonorrhea in this study, the limited protection against this STI is a vexing concern.
“Quarterly gonorrhea positivity ranged from 7.6% (95% CI, 6.2%-9.5%) to 11.3% (95% CI, 9.7%-13.1%) before starting doxyPEP and from 7.8% (95% CI, 6.4%-9.5%) to 10.7% (95% CI, 7.1%-16.1%) after starting doxyPEP,” the authors wrote. “Overall, mean gonorrhea positivity declined from 10.2% (95% CI, 9.6%-10.9%) before starting doxyPEP to 9.0% (95% CI, 8.0%-10.1%) after starting doxyPEP (RR, 0.88; 95% CI, 0.77-1.00; P = .048).”
Other studies looking at doxyPEP and doxyPrEP have shown limited protection against it as well.
Overall, the investigators offered a positive conclusion. “These findings suggest that doxyPEP may offer substantial benefits for reducing population-level STI transmission with broader implementation,” the authors wrote.
Reference
1.Traeger MW, Leyden WA, Volk JE, et al. Doxycycline Postexposure Prophylaxis and Bacterial Sexually Transmitted Infections Among Individuals Using HIV Preexposure Prophylaxis. JAMA Intern Med. Published online January 06, 2025. doi:10.1001/jamainternmed.2024.7186
