Seroepidemiology of Varicella zoster in Israel prior to large-scale use of varicella vaccines

Objectives: This large-scale study provides up-to-date estimates of Varicella zoster virus (VZV) age-specific seroprevalence and characteristics of VZV transmission in a representative sample of the Israeli population. Methods: In 2000-2001, 1,642 sera collected from an age-stratified general population sample were tested for VZV antibodies using an indirect IgG ELISA system. Results: The age-weighted VZV overall estimate was 90.2%. Seropositivity increased rapidly with age, from 68.9% at age 4 to 94.4% at age 7 and 96.6% at age 12 years. The highest force of infection was in the 4-5 years age group (0.548 per susceptible year) followed by the 6-9 years age group. Multivariate analysis revealed that VZV seroprevalence estimates were significantly associated with age and place of origin. The highest seroprevalence estimate was found among subjects of Eastern origin. Conclusions: The seroepidemiology of VZV in Israel shows a pattern corresponding to that described for developed European countries. This study indicates that the highest force of infection is in pre-school children. Knowledge of pre-vaccination seroepidemiology is important to evaluate the effect of vaccination programs on the epidemiology of the disease.