Abstract
Varicella-zoster virus (VZV) causes chickenpox and reactivation of latent VZV causes herpes zoster (HZ). VZV reactivation is subject to the opposing mechanisms of declining and boosted VZV-specific cellular mediated immunity (CMI). A reduction in exogenous re-exposure 'opportunities' through universal chickenpox vaccination could therefore lead to an increase in HZ incidence. We present the first individual-based model that integrates within-host data on VZV-CMI and between-host transmission data to simulate HZ incidence. This model allows estimating currently unknown pivotal biomedical parameters, including the duration of exogenous boosting at 2 years, with a peak threefold to fourfold increase of VZV-CMI; the VZV weekly reactivation probability at 5% and VZV subclinical reactivation having no effect on VZV-CMI. A 100% effective chickenpox vaccine given to 1 year olds would cause a 1.75 times peak increase in HZ 31 years after implementation. This increase is predicted to occur mainly in younger age groups than is currently assumed.
Highlights
Varicella-zoster virus (VZV) causes the itching, erythematous vesicular disease called varicella or chickenpox, mainly during childhood, and remains latent in neural ganglia afterwards
Using a step-wise algorithm we initially found eight unique parameter sets leading to a reasonable fit of Belgian herpes zoster (HZ) incidence data
It is hypothesized that exogenous re-exposure to varicella increases VZV-specific cellular immunity (VZV-cellular mediated immunity (CMI))
Summary
Varicella-zoster virus (VZV) causes the itching, erythematous vesicular disease called varicella or chickenpox, mainly during childhood, and remains latent in neural ganglia afterwards. VZV reactivations may cause herpes zoster (HZ), which presents clinically as a painful dermatomal rash. Recent research supports the hypothesis that waning of VZV cellular mediated immunity (CMI) by age is influenced by cytomegalovirus (CMV) infection (Ogunjimi et al, 2014). In many other countries policy makers have been hesitant to introduce childhood VZV vaccination due to the general population’s perception of varicella as a relatively mild disease, as well as the so-called exogenous boosting hypothesis
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