Varicella vaccine has been extensively studied in Japan, the United States and Canada since 1974. Its efficacy in healthy children is good, on the order of 94%. It also has a good efficacy in immunocompromised children, such as children treated for acute leukemia or malignant tumors. However, the vaccine has to be administrated during a 2-3 week transient suppression of chemotherapy. In the USA, varicella vaccination is recommended for receptive adults who are particularly exposed to varicella, such as health professionals working with immunocompromised patients. Benefits and cost analysis of a generalized varicella vaccination in children has shown that it would be beneficial due to the cost of parents' work leave during the children's illness.