Risk of herpes zoster in adults immunized with varicella vaccine.

A program of routine varicella vaccination of children 12-18 months of age, begun in the United States in 1995, has been very successful in reducing the incidence of varicella. Varicella-zoster virus (VZV), in both wild-type and live attenuated forms, is notable for its ability to produce latent infection of sensory neurons from which it can later reactivate to cause herpes zoster (HZ). Therefore, the effects of vaccination on this secondary VZV-related disease are important to consider; in practice, however, such studies are complicated by the typically long delay between acquisition of the virus and its reactivation. Studies of immunocompromised children have shown that vaccination is relatively protective against HZ in this highly vulnerable group. We now present long-term follow-up data on a group of individuals who received varicella vaccine as healthy young adults 10-26 years ago and who have been followed prospectively by means of active surveillance. Among some 2000 person-years of follow-up, 2 cases of HZ have occurred, for a rate of 1.00 case/1000 person-years. Overall, the incidence of HZ in this cohort, therefore, is similar to published data for the US population in the prevaccine era.