Daily oral pre-exposure prophylaxis (PrEP) is highly effective in preventing HIV infection when used appropriately. Clinical studies have concluded
that daily oral tenofovir/emtricitabine (TDF/FTC) use can reduce the risk of acquiring HIV through sex by about 99%.
However, research has also demonstrated that poor adherence to PrEP can result in reduced efficacy and can also lead to HIV-drug resistance if an individual becomes infected while using PrEP.
Since adherence is a key element of the PrEP regimen, investigators with the US Centers for Disease Control and Prevention’s Division of HIV/AIDS Prevention conducted a new study to estimate PrEP persistence among cohorts of individuals with commercial or Medicaid insurance. Their findings were published in Clinical Infectious Diseases
The study team analyzed data from the IBM MarketScan Research Database focusing on individuals aged 18-64 years who initiated PrEP between 2012-17. In total, the team studied 11,807 commercially-insured and 647 Medicaid-insured persons with PrEP prescriptions.
In order to determine PrEP persistence, the team calculated the time period that each individual continued to fill their prescriptions until there was gap of more than 30 days.
From there, Kaplan-Meier time-to-event methods were used to determine estimates of the proportion of individuals who persisted with PrEP at 3, 6, and 12 months following initiation of the regimen.
According to the results, commercially-insured patients persisted for median time of 13.7 months (95% CI, 13.1-14.1), compared with 6.8 months (95% CI, 6.1-7.6) among Medicaid patients.
The investigators also designed Cox proportional hazards models to determine characteristics associated with non-persistence.
The characteristics of being female, younger in age, residing in a rural area, and black race were linked to shorter persistence of PrEP.
The study team adjusted for covariates and found that female sex [hazard ratio, 1.18; 95% CI, 1.56-2.11) and younger age (18-24 years: HR, 2.38; 95% CI, 2.11-2.69) predicted non-persistence.
The lack of persistence in females could be a concerning topic. In 2017, 19% of new HIV diagnoses occurred in women. According to the authors of this report, an estimated 176,670 women have indications for PrEP in the United States yet only 2% have been prescribed TDF/FTC.
Some barriers to PrEP for women have been identified as low HIV risk perception. The team points to the need for more research on the relationship between pregnancy and PrEP use.
One notable limitation of this research is that persistence was based upon prescription fill records, but an individual may not be adherent to medication just because they filled their prescription.
Overall, the study found that more than half of commercially-insured persons who initiated PrEP persisted with it for 12 months, compared with a third of those with Medicaid.
“A better understanding of reasons for non-persistence is important to support persistent PrEP use and to develop interventions designed for the diverse needs of at-risk populations,” the authors concluded. “PrEP will only be effective in preventing new HIV infections if it is used adherently and persistently by persons at risk of acquiring HIV.”
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