Modeling Individual Heterogeneity for Recurrent Infections

• Activity Number: 492
• Type: Contributed
• Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Niel Hens*+ and Steven Abrams
• Companies: Hasselt University and Hasselt University
• Keywords: shared and correlated gamma frailty models ; current status data ; mass action principle ; reproduction number

Abstract

In recent years, it has been shown that individual heterogeneity in the acquisition of infectious diseases has a large impact on the estimation of important epidemiological parameters such as the reproduction number. Therefore frailty modeling has become increasingly popular in infectious disease epidemiology. However, so far, using frailty models, it was assumed infections confer lifelong immunity after recovery, an assumption which is untenable for non-immunizing infections. Our work concentrates on refining the existing frailty models to encompass complexities of reinfections and waning immunity while accounting for individual heterogeneity. Shared gamma frailty models, which are frequently used in practice, and correlated gamma frailty models that have proven to be a valuable alternative are considered. Misspecification of the underlying infection process is quantified in terms of the estimation of the reproduction number. We show that assuming lifelong immunity when applying frailty models introduces substantial bias in the estimation of these quantities. We illustrate our work using cross-sectional serological data on parvovirus B19 and varicella zoster virus from Belgium.