Bacterial STIs are concentrated in subgroups of MSM using PrEP, according to results published in AIDS. Elske Hoornenborg, MD, and colleagues examined rates of urogenital, anal, and pharyngeal chlamydia and gonorrhea, as well as syphilis, among participants (N=366) in a PrEP demonstration project. They identified three courses of STI incidence: “low overall,” or a mean of approximately 0.1 STI every 3 months (52%); “medium overall,” or a mean of 0.4 STI every 3 months (43%); and “high and fluctuating,” or an incidence of 0.3 to 1 STIs every 3 months (5%). People in the low overall group were significantly older and reported less chemsex and condomless anal sex with casual partners than participants in the other trajectories. Participants in the “high and fluctuating” and “medium overall” groups accounted for 23% and 64% of all STIs, respectively, seen during follow-up. “STI incidence was concentrated in subpopulations of PrEP users who were younger [and] had more chemsex and condomless anal sex,” Dr. Hoornenborg and colleagues wrote. “Screening frequency for STIs could be reduced for subpopulations with low risk for incident STIs.”
