Whether intermittent PrEP provides similar coverage of sex events compared to daily PrEP is still unclear. We wished to assess in the setting of the ANRS IPERGAY trial among men who have sex with men (MSM), the coverage of sex events with «on demand» event-based PrEP.
A 2-month sub-study was proposed to participants (pts) enrolled in the open-label phase of the trial. On demand TDF/FTC dosing regimen included two pills within 2-24h before sex, one pill 24h later and a last pill 48h after the first drug intake. Pts received an electronic MEMS device to record each bottle opening. Questionnaires collected information on daily PrEP intake and sexual behavior by text messages and computer assisted self-interviews. Adherence was also measured by pill count. PrEP full coverage was defined by ≥ 1 pill taken within 24 hours before sex and 1 pill taken within 48 hours following sex, and partial coverage as either one. Two groups of pts were defined according to the number of bottle openings: those who used intermittent PrEP (< 5 openings per week) and those using daily PrEP (≥ 5 openings per week).
From March 1st, 2016 to May 3rd, 2016, the study was proposed to 228 pts and 54 pts were enrolled, all MSM with a median age of 41 years. Pts reported 361 sex events with a median of 4 sex events/pt/month (IQR: 2-8), 81 oral sex only (23%), 279 anal sex (77%) and one unknown. Among the 154 receptive anal sex events, 80% (124) were condomless. There was a strong correlation (r=0.92) between bottle openings and pill count. Forty-two pts (78%) used intermittent PrEP and 12 (22%) used daily PrEP, median number of bottle openings/month of 11.5 (IQR: 4-16) and 24.9 (IQR: 24-27) respectively (p<0.0001). Coverage of sex events is reported in the Table.
Reported PrEP coverage of sex events was high both with daily and intermittent PrEP. In the MSM using intermittent PrEP, coverage increased with at-risk practices and was highest for condomless receptive anal sex.