How Does Adherence of Daily Dosing vs Event-Driven PrEP Regimens Compare?

In a study looking at PrEP usage in men who have sex with men (MSM), and measuring event-driven usage vs daily dosing, the former increased and the latter decreased over a 1 year period.

The data from the study, Effectiveness and Medication Adherence of Daily and Event-Driven Pre-Exposure Prophylaxis Regimens among Chinese Men who have Sex with Men: a Real-world CROPrEP study was presented at the 11th International AIDS Society Conference on HIV Science.

From December 2018 to October 2020, Chinese investigators offered PrEP to MSM with a self-chosen regimen of daily or event-driven TDF/FTC in 4 cities including Beijing, Shenyang, Chongqing, and Shenzhen.

The PrEP users were followed up with every 3 months up to 1 year. The investigators reported PrEP adherence by measuring the proportion of covered sex acts by PrEP.

In the study, 520 MSM chose using a daily dosing regimen and 503 decided upon an event-driven regimen. In addition, 507 other MSM were PrEP non-users. In terms of the 12-month follow-up, 88% of PrEP users and 89% of the non-users completed it.

Contrary to what some might expect in thinking that daily dosing would have greater adherence, the results showed that event-driven regimens increased and people using daily dosing decreased.

“The proportion of covered sex acts by PrEP increased over time in event-driven PrEP users (from 57% to 78%), while the opposite trend was observed in the daily group (75% to 72%),” the investigators reported.

Still the two regimens remain important. “This real-world study showed that PrEP can effectively reduce HIV risk among MSM,” investigators wrote. “Compared with the traditional daily medication regimen, the event-driven regimen has increased trend of medication adherence and a better HIV protective effect.”