The effects of vaccination in an age-dependent model for varicella and herpes zoster

The varicella-zoster virus (VZV) is responsible for the infectious diseases varicella and herpes zoster, more commonly known as chickenpox and shingles. The United States Food and Drug Administration recently approved a VZV vaccine for use in children to prevent chickenpox. The VZV vaccine was tested in Japan, Korea, and the United States, and these extensive experimental investigations led to final approval in the United States. In this paper, an age-dependent model for varicella and herpes zoster is formulated. Using statistics for the United States, parameter values for the model are estimated and numerical solutions are calculated. The effects of various control strategies, designed to decrease the number of individuals susceptible to varicella and zoster, are investigated. In particular, the effect of vaccination on the average age of infection, the average number of infections per person during their lifetime, and the ratio of number of tester cases after control to those before control are investigated.