Measuring the Potential Role of Frailty in Apparent Declining Efficacy of Hiv Interventions

• Activity Number: 19
• Type: Topic Contributed
• Date/Time: Sunday, August 3, 2014 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Felicia P. Hardnett *+ and Charles Rose
• Companies: CDC and CDC
• Keywords: HIV Intervention Trials ; Vaccine Waning ; HIV Prevention

Abstract

Results of recent HIV intervention trials have been challenging to interpret because efficacies of the interventions appear to decline over time. Researchers have attributed the declining efficacy to a loss of vaccine efficacy (or "waning") or decreased adherence to HIV prevention methods (e.g., microbicides, condoms). Heterogeneity in infection risk (or "frailty") is another possible explanation. We measure the potential impact of frailty on measures of intervention efficacy in randomized controlled-trials of HIV interventions. We designed several study scenarios that held study-related factors constant (e.g., sample size, follow-up time). By varying both the waning and frailty parameters, we quantified the percent change in incidence attributable to frailty and then measured the change in the incidence rate ratio (IRR) attributable to frailty. We found that frailty alone can impact disease incidence over time. However, frailty isn't likely to have a major impact on the IRR. The factor which has the greatest influence on the IRR over time is the intervention itself and the degree to which it is allowed to wane.