Although TDF/FTC Pre-Exposure Prophylaxis (PrEP) was approved for daily use to prevent HIV transmission in at risk men who have sex with men (MSM), some may have discrete periods of high risk (e.g. on vacation), and this use has not been previously evaluated. The current study evaluated the feasibility of short term, fixed interval PrEP.
Participants agreed to participate in an open label study of TDF/FTC plus a focused behavioral intervention. At least 2-weeks prior to vacation participants received a single session cognitive behavioral therapy–based intervention and were given a 30-day supply of TDF/FTC and instructed to adhere to daily dosing starting 7-days prior to vacation through 7-days post vacation. Adherence was assessed via self-report and plasma TFV concentration levels within 3-days post-vacation. Safety labs and behavioral assessments were collected at baseline, post-trip, and at 3-months.
54 participants were enrolled in Boston and Pittsburgh, of which 48 completed the post-vacation visit. Participants were mostly white (72.2%), had a mean age of 30.0 (range 24-64), 83.3% identified as gay, and 68.5% were employed full-time. Only 3 individuals (6.3%) had drug levels below protective levels (≤4 daily doses during the week). There was high concordance between biological markers and self-reported adherence with 95.8% reporting their ability to take daily PrEP as excellent or very good; 6 participants reported missing 2 or fewer doses and only 1 participant missing six of seven doses. Of the 3 people with less than protective levels of drug, none reported drug use. 55.5% of participants reported being likely or very likely to remain on PrEP after the study. 1 participant became HIV-infected more than 2 months after vacation because of lapse in insurance to cover ongoing PrEP; no other did after 3 months of follow-up. 77% of the sample reported condomless sex during 1 to 14 of their vacation days. All who reported condomless sex were adherent to PrEP except for 1 participant who reported partial PrEP use and condomless sex on 8 days.
These findings suggest that most MSM can be adherent to short-term fixed-interval episodic PrEP (Epi-PrEP) during short high risk vacation periods. Time-limited dosing strategies may be a realistic, feasible, acceptable and useful option for some high-risk MSM whose behaviors are episodic, but non-random. For others, initiating PrEP on vacation may provide a helpful way to initiate long term PrEP.