Early Reconstitution of Immunity and Decreased Severity of Herpes Zoster in Bone Marrow Transplant Recipients Immunized with Inactivated Varicella Vaccine

Varicella-zoster virus (VZV) causes herpes zoster after bone marrow transplantation (BMT). The immunogenicity of heat-inactivated varicella vaccine and effects on VZV pathogenesis were evaluated in 75 BMT patients randomized to receive vaccine or no intervention. Among 14 patients given a single dose at 1 month after transplantation, the mean (±SE) stimulation index (SI) was 12.20 ± 3.13 compared with 4.83 ± 2.74 (P = .036) in 14 unvaccinated patients, but clinical disease was not altered. Among 24 patients vaccinated at 1, 2, and 3 months, mean SI was 8.43 ± 3.89 versus 2.00 ± 0.33 (P = .014) in 23 unvaccinated patients at 4 months and 8.56 ± 2.81 versus 5.30 ± 2.47 (P = .043) at 5 months. Disease severity associated with VZV reactivation was decreased dramatically in vaccinees given three doses; severity scores were 6.4 ± 1.0 versus 11.8 ± 1.1 (P = .007). This experience with varicella vaccine in BMT patients is the first evidence that active immunization can reduce morbidity due to herpesvirus reactivation in high-risk populations.