Varicella is a disease of children that was differentiated clinically from smallpox about 200 years ago. It is now known to be a herpesvirus. The relationship of varicella to zoster was first described by Von Bokay.1 He postulated that both were caused by the same agent when he noted that chickenpox frequently followed exposure to zoster. That a single agent was responsible for both conditions was confirmed by Weller and Stoddard2 who first propagated virus from patients with varicella and zoster in cell cultures; they3 subsequently demonstrated that the antibody produced following zoster or varicella reacted with the same antigen. Indeed, Brunell and his co-workers4 were able to show that globulin extracted from the serum of patients with zoster protected exposed children from varicella.In 1974, Takahashi and his colleagues5 published the first report of his chickenpox vaccine. They found that normal children were protected against infection if the vaccine was given prior to or even three days following exposure; the vaccine was essentially devoid of side effects. Subsequently, Izawa et al6 tested the vaccine in children with leukemia, demonstrating both its safety and effectiveness. Many investigators have confirmed the observations of those investigators during the ensuing 10 years.This experience must now be used to determine whether and how live varicella vaccine should be used (1) in children with leukemia, (2) universally in normal children, and (3) in susceptible adults.The reticence to use the vaccine in normal children has been because of the lack of experience with live herpesvirus vaccines.7
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