Characterization of HIV Preexposure Prophylaxis Use Behaviors and HIV Incidence Among US Adults in an Integrated Health Care System

IMPORTANCE: Long-term follow-up is needed to evaluate gaps in HIV preexposure prophylaxis (PrEP) care delivery and to identify individuals at risk for falling out of care. OBJECTIVE: To characterize the PrEP continuum of care, including prescription, initiation, discontinuation, and reinitiation, and evaluate incident HIV infections. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study used data from the electronic health records (EHR) at Kaiser Permanente Northern California to identify individuals aged 18 years and older who received PrEP care between July 2012 and March 2019. Individuals were followed up from date of linkage (defined as a PrEP referral or PrEP-coded encounter) until March 2019, HIV diagnosis, discontinuation of health plan membership, or death. Data were analyzed from December 2019 to January 2021. EXPOSURES: Sociodemographic factors included age, sex, race and ethnicity, and neighborhood deprivation index, and clinical characteristics were extracted from the EHR. MAIN OUTCOMES AND MEASURES: The primary outcomes were attrition at each step of the PrEP continuum of care and incident HIV infections. RESULTS: Among 13 906 individuals linked to PrEP care, the median (interquartile range [IQR]) age was 33 (27-43) years, 6771 individuals (48.7%) were White, and 13 227 (95.1%) were men. Total follow-up was 26 210 person-years (median [IQR], 1.6 [0.7-2.8] years). Of individuals linked to PrEP care, 88.1% (95% CI, 86.1%-89.9%) were prescribed PrEP and of these, 98.2% (95% CI, 97.2%-98.8%) initiated PrEP. After PrEP initiation, 52.2% (95% CI, 48.9%-55.7%) discontinued PrEP at least once during the study period, and 60.2% (95% CI, 52.2%-68.3%) of these individuals subsequently reinitiated. Compared with individuals aged 18 to 25 years, older individuals were more likely to receive a PrEP prescription (eg, age >45 years: hazard ratio [HR], 1.21 [95% CI, 1.14-1.29]) and initiate PrEP (eg, age >45 years: HR, 1.09 [95% CI, 1.02-1.16]) and less likely to discontinue (eg, age >45 years: HR, 0.46 [95% CI, 0.42-0.52]). Compared with White patients, African American and Latinx individuals were less likely to receive a PrEP prescription (African American: HR, 0.74 [95% CI, 0.69-0.81]; Latinx: HR, 0.88 [95% CI, 0.84-0.93]) and initiate PrEP (African American: HR, 0.87 [95% CI, 0.80-0.95]; Latinx: HR, 0.90 [95% CI, 0.86-0.95]) and more likely to discontinue (African American: HR, 1.36 [95% CI, 1.17-1.57]; Latinx: 1.33 [95% CI, 1.22-1.46]). Similarly, women, individuals with lower neighborhood-level socioeconomic status (SES), and persons with a substance use disorder (SUD) were less likely to be prescribed (women: HR, 0.56 [95% CI, 0.50-0.62]; lowest SES: HR, 0.72 [95% CI, 0.68-0.76]; SUD: HR, 0.88 [95% CI, 0.82-0.94]) and initiate PrEP (women: HR, 0.71 [95% CI, 0.64-0.80]; lower SES: HR, 0.93 [95% CI, 0.87-.0.99]; SUD: HR, 0.88 [95% CI, 0.81-0.95]) and more likely to discontinue (women: HR, 1.99 [95% CI, 1.67-2.38]); lower SES: HR, 1.40 [95% CI, 1.26-1.57]; SUD: HR, 1.23 [95% CI, 1.09-1.39]). HIV incidence was highest among individuals who discontinued PrEP and did not reinitiate PrEP (1.28 [95% CI, 0.93-1.76] infections per 100 person-years). CONCLUSIONS AND RELEVANCE: These findings suggest that gaps in the PrEP care continuum were concentrated in populations disproportionately impacted by HIV, including African American individuals, Latinx individuals, young adults (aged 18-25 years), and individuals with SUD. Comprehensive strategies to improve PrEP continuum outcomes are needed to maximize PrEP impact and equity.