Mathematical Theory and Modeling www.iiste.org ISSN 2224-5804 (Paper) ISSN 2225-0522 (Online) Vol.4, No.8, 2014 46 Modeling the Impact of Immunization on the Epidemiology of Varicella Zoster Virus. Stephen Edward 1* , Dmitry Kuznetsov 1 and Silas Mirau 1 1 School of CoCSE, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, *E-mail of the corresponding author: edwards@nm-aist.ac.tz Abstract Chickenpox (also called varicella) is a disease caused by virus known as varicella-zoster virus (VZV) also known as human herpes virus 3. In this paper, a deterministic mathematical model for transmission dynamics of VZV with vaccination is formulated. The effective reproduction number is computed in order to measure the relative impact for individual or combined intervention for effective disease control. Numerical simulations of the basic reproduction number of the model shows that, the combination of vaccination and treatment is the most effective way to combat the epidemiology of VZV in the community. Keywords: Modeling, Treatment, Vaccination, Epidemiology. 1. Introduction Chickenpox (also called varicella) is a disease caused by virus known as varicella-zoster virus (VZV) also known as human herpes virus 3 (HHV -3) (Almuneef , 2006) . In non-vaccinated populations, primary infections tend to occur at a younger age (Gerson, 2008). The main symptoms of chickenpox are fever, headache, stomach ache,itchy rash especially in the mouth, on chest, abdomen, back, face and upper arms and legs. The rash starts as small red spot, difficult breathing, malaise and anorexia. Chickenpox is widely transmitted from touching the fluids from chickenpox blister. The virus is spread either by direct contact with a person with active chickenpox or shingles, or by direct contact with clothes or other articles infected with vesicle fluid, saliva, nasal discharge etc, or by air borne spread of small droplets of infected mucous of fluid. There are different notions to the origin of the name of this disease. One is, once infected; the skin appeared as picked by chicken. Another is the rash resembles the seeds of Chick Peas. Most common explanation is that the disease is not that much dangerous compared to small pox so it is a ‘chicken’ version of pox. The occurrence of chicken pox is different in different geographical zones. In temperate countries chickenpox is usually a mild, self-limiting infection, affecting pre-school children (Vyse, 2004), however, the incidence of chickenpox in these areas is increasing in adolescents and adults (Fairley &Miller, 1996), which may in part be due to increased world travel and economic migration of susceptible individuals. In many tropical countries the epidemiology is different, with about 60% of adults being immune (Lee, 1998). In the past, the varicella zoster virus affected virtually the entire population and had substantial morbidity and mortality associated with both primary varicella and herpes zoster reactivation. Since the varicella vaccine was first approved in 1995, there has been a significant decline in incidence, morbidity, and mortality caused by primary varicella. Breakthrough disease with the one-dose vaccine schedule led to the recommendation in 2006 that children receive a two-dose vaccine series. Older adults have also benefited from the development of the