Real-world data from a large American chain of retail pharmacies show that only two in five people keep on taking pre-exposure prophylaxis (PrEP) for two years after starting, researchers report in the Journal of the International AIDS Society this week.
Most studies of PrEP persistence have been for shorter periods of time, but it has been thought that if participants are retained past an initial period on PrEP, then they are more likely to stick with it. The new study does not support that.
The researchers analysed pharmacy fill records from a random sample of 7148 people who started PrEP at a Walgreens branch in 2015 (perhaps one in ten American PrEP users). Data were collected for two years after starting the preventative treatment. PrEP persistence was defined as having at least 16 days of PrEP medication filled per month for at least three-quarters of the months (e.g. nine months in a year). The threshold of 16 days per month was chosen because dosing at least four days per week has been shown to offer substantial protection against HIV to men who have sex with men.
The vast majority of PrEP users were men (97%). Most were in their thirties or forties, and 80% had commercial insurance.
- Over the first 12 months, 56% (4030/7148) were classified as persistent on PrEP.
- Amongst those who were persistent in the first year, 63% (2521/4030) were persistent during months 13 to 24.
- Throughout the first 24 months, 41% (2951/7148) were persistent (i.e. they had prescriptions for 18 of the 24 months).
People have ‘seasons of risk’, so not all PrEP users would need to stay on PrEP for the full two years. “But this is unlikely to be the only factor accounting for such high levels of PrEP cessation,” the authors comment. “Such substantial behaviour modification to convert three-fifths of individuals initiating PrEP to be no longer PrEP eligible is highly unlikely.”
In multivariable analysis, male gender, being 25 years of older, having a copay of $20 or less, having commercial insurance, and attending a community-based specialty pharmacy from the national chain were associated with persistence.
Only 29% of people aged 18 to 25 stayed on PrEP throughout the two years. “Younger individuals may be more likely to experience challenges in a number of areas, including cost navigation, fear of disclosure due to use of parental insurance, limited experience with the healthcare system, and financial barriers,” comment the authors.
Comparable studies of PrEP persistence have not been conducted in settings with fewer financial and administrative barriers to accessing healthcare.
As individuals switching to a different pharmacy could be misclassified as discontinuing PrEP, the researchers conducted a sensitivity analysis which only included the 5837 people who filled a prescription at the chain for something apart from PrEP, after the 24-month study period. This made little difference to the results, indicating that pharmacy switching is not an important factor.
