Background: Sexually transmitted infections (STIs) are common in people using pre-exposure prophylaxis (PrEP). We examined risk and factors associated with STIs in a cohort of PrEP users in an integrated health system in the United States.
Setting: The Kaiser Permanente Southern California is a large integrated health system that provides comprehensive medical services to approximately 4.7 million demographically diverse members.
Methods: We identified men and transgender women initiating PrEP between January 1, 2014, and June 1, 2018, and followed through December 31, 2018. Demographic and clinical factors potentially associated with the risk of bacterial STIs during PrEP use were evaluated using Poisson regression models.
Results: Among 5042 individuals tested for STIs with 7198 person-years of follow-up, 1709 (33.9%) had at least one new STI. The estimated incidence of STIs was 48.3 per 100 person-years, and the most common STI was rectal chlamydia. Most repeat STIs (61.4%) occurred <180 days apart. In a multivariable analysis, an history of STIs in the prior 6 months through 7 days after the PrEP initiation was the most prominent risk factor of STIs during PrEP use (adjusted risk ratio: 1.78, 95% confidence intervals: 1.65 to 1.93). Other risk factors included younger age (<35 years), being Hispanic, and having a history of alcohol use disorder or drug use disorder.
Conclusions: Quarterly STI testing and targeted intervention to mitigate STI risk are warranted for young and racial minority PrEP users, particularly for those with prior history of STIs and substance use disorders.
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