Humoral and cellular immune responses to whole varicella-zoster virus (VZV) antigen and the VZV proteins glycoprotein I (gpI) and nonglycosylated protein p170 were evaluated in healthy children and adults given lyophilized live-attenuated varicella vaccine. Children received one dose of vaccine containing 950 pfu, whereas adults received two doses of 2500 pfu. After one year, the antibody titers of adult vaccinees to whole VZV and to gpI were significantly higher than those of children. Antibody titers to whole VZV, gpI, and p170 were lower among both vaccine populations than titers in naturally immune individuals, but vaccinees who seroconverted initially retained detectable VZV antibodies. Using T lymphocyte proliferation to measure cellular immunity, we found the mean (+/- SE) transformation index to whole VZV antigen to be 4.1 +/- 0.96 in children tested at one year, a mean significantly lower than the mean of 12.7 +/- 3.39 in adults and 13.0 +/- 1.67 in naturally immune subjects. These observations suggest that the vaccine dose affects vaccine-induced immunity to VZV.