Adherence to different pre-exposure prophylaxis (PrEP) dosing schedules can vary significantly depending on a person's sex and geographical region, according to a pair of recently published studies that compared PrEP coverage on a daily pill, a time-driven schedule (two pills per week, plus one after sex) and an event-driven one (one pill before and after sex).
One study found that men who have sex with men (MSM) and transgender women in Bangkok, Thailand, who were assigned to take nondaily doses of PrEP achieved a level of HIV protection comparable to daily PrEP, but the same populations in the Harlem neighborhood of New York City did not. The findings were published in Clinical Infectious Diseases.
Meanwhile, an assigned daily dosing schedule for PrEP appeared to be more effective among South African women than a time-driven schedule and an event-driven schedule , according to a trial published in The Lancet.
Both studies were conducted before the IPERGAY trial established the efficacy of nondaily PrEP. Study authors hypothesized that adherence to the nondaily regimens may have been better, had the IPERGAY results been known. They also suggested that the results could have been affected by demographic and site-specific differences between Bangkok and Harlem, as well as women's difficulty in planning for sex compared to men in South Africa.
Barbara Jungwirth is a freelance writer and translator based in New York. Follow Barbara on Twitter: @reliabletran.
Myles Helfand is the executive editor and general manager of TheBody.com and TheBodyPRO.com. Follow Myles on Twitter: @MylesatTheBody.