Early Adopters of Event-driven Human Immunodeficiency Virus Pre-exposure Prophylaxis in a Large Healthcare System in San Francisco.

Among 279 patients within a large healthcare system in San Francisco, event-driven HIV pre-exposure prophylaxis using a 2-1-1 regimen was a desirable alternative to daily dosing. Problems with adherence, planning sex in advance, or side effects were infrequent (13.9%). We found no new HIV infections over 136 person-years of follow-up.