Immunity to varicella zoster virus in young Israeli adults

Background: Chickenpox is a highly contagious childhood infection caused by varicella zoster virus, a virus of the herpes family. Although a mild and self-limiting disease in otherwise healthy children, chickenpox can be a complicated and even life-threatening disease in adults, pregnant women and immunosuppressed individuals. Among infants whose mothers had varicella during the first trimester of pregnancy, 2-3% will develop a congenital VZV syndrome that includes a combination of scarring, limb deformation, central nervous system impairment and ocular injury. In 1974, a live attenuated virus vaccine against VZV was developed in Japan and has been thoroughly tested for safety, efficacy and long-term effects. In March 1995 the vaccine was licensed in the U.S. for use in healthy children only. Objectives: To determine the rate of immunity to VZV in young Israeli adults. Methods: On the assumption that a randomly picked a sample of 18-year-old army recruits in Israel is representative of the general Jewish population, 900 sera samples were taken for 3 years (1985, 1988, 1992). The sera were analyzed for IgG to VZV with a commercial ELISA kit using microwells coated with VZV antigens. Results: A total of 98% of the samples tested positive for VZV antibodies. The difference in serologic values between the recruitment years was not statistically significant. Conclusion: The majority of the Israeli population reaches adulthood already immunized against VZV, with immigrants having slightly lower immunity rates. Nonetheless, a few dozen cases of chickenpox are diagnosed in the IDF annually. These data should be taken into account when a vaccination program is devised. Should such a program be implemented, it would be interesting to repeat the serosurvey for comparison. A shift in the peak occurrence age might necessitate the administration of a booster vaccine at an older age.