The Safety of Oka Varicella in Children Prior to Solid Organ Transplantation

Inclusion Criteria: * Children \> 9 months of age and adolescents \< 18 years of age. * Pediatric transplant candidates who are in any of the following categories: 1. listed to receive kidney, liver, heart, lung or other or solid organ transplantation in a Canadian transplant centre 2. not yet officially listed, but are regarded by their physicians as transplant candidates by virtue of their underlying diseases * No clinical history for varicella. * Seronegative for antibodies to VZV except infants 9 - 12 months of age who may be seropositive due to maternal antibodies. * Informed consent obtained Exclusion Criteria: * Previous immunization with varicella vaccine. * Any established immune deficiency (underlying disease or drug induced) or any neoplastic disease * Children on any oral and / or intravenous steroids within 3 months prior to immunization. Children on inhaled corticosteroids in excess of 800 mcg of beclomethasone dipropionate ( or equivalent ) per day. * Any exposure to varicella or herpes zoster in the previous 4 weeks involving household, playmate or hospital contacts. * Inability to delay the transplantation for up to 6 weeks following the last varicella immunization. * Presence of a person at increased risk for varicella infection in direct and unavoidable proximity with the vaccinees ( e.g. an immunocompromised sibling) * Past history of varicella or known positive antibody titer for varicella except infants 9 - 12 months of ages who may be seropositive due to maternal antibodies * Known hypersensitivity to any of the components of the vaccine, including neomycin and gelatin * Patients whose mothers are known to be seronegative and plan to become pregnant in the subsequent three months * Administration of VZIG or any other blood products in the previous six weeks (packed red blood cells excepted). * Any significant infection and/or fever at the time of vaccination * Any patient receiving or planning to receive salicylates in the six weeks after immunization * Any patient who has received any live vaccine for 6 weeks or killed vaccine for 2 weeks prior to or after the scheduled VARIVAX™ vaccination.