SAFETY AND CELLULAR AND HUMORAL IMMUNE-RESPONSES OF A BOOSTER DOSE OFVARICELLA VACCINE 6 YEARS AFTER PRIMARY IMMUNIZATION

Four hundred nineteen children and adolescents immunized with live var icella vaccine 4-6 years earlier were enrolled in a study to evaluate the safety and immune response to a booster dose containing similar to 3300 pfu of virus. Of the subjects, 99% (414/419) maintained antibody to varicella tester virus (VZV) with a geometric mean titer of 25.7 a nd mean stimulation index (SI) for VZV-specific lymphoproliferation re sponse of 40.3 +/- 5.3 (SE). Some 7-10 days after the booster immuniza tion, seropositivity rates increased to 100% (302/302), and GMT was 14 3.6 (anamnestic response). At 6 weeks after the booster inoculation, a subset of subjects had 100% seropositivity (74/74) with a GMT of 218. 8 and an SI of 58.6. After 3 months, seropositivity was 100% (358/358) , GMT was 119.0, and SI was 61.4.