This study compared safety, tolerability, and immunogenicity of the Oka/Merck varicella vaccine and VARILRIX [Oka-RIT strain SmithKline Beecham Biologicals] in healthy children 12-24 months of age. Subjects were randomized in this double blind study to receive either a single dose of Oka/Merck varicella vaccine, (approximately 50,000 plaque forming units (PFU), Group A or approximately 16,000 PFU, Group B) or 1 dose of VARILRIX, (approximately 40,000 PFU/dose, Group C). Safety profiles in each treatment group were similar. The proportions of subjects achieving a 6-week postvaccination titer> or = 5 gpELISA units in Groups A, B or C were 97.1, 95.2 and 85.6%, respectively.