Immunogenicity of a two-dose regime of varicella vaccine in children with cancers

Objectivc: Live-attenuated varicella vaccine is effective and safe in immunocompetent children. In this study, we assess the immunogenicity and adverse events following varicella vaccination in immunosuppressed cancer children. Methods: Varicella-zoster virus (VZV)-seronegative cancer children received two doses of live-attenuated VZV vaccine (Varilrix(R)) in a span of 3 months. Patients with lymphoblastic leukaemia (ALL) were in the maintenance phase of chemotherapy, whereas those with solid tumours joined the study around 3-6 months from treatment discontinuation. VZV-specific cellular and humoral immune responses were measured before and after VZV vaccination. Results: The median (range) age of the 17 was 4.4 yr (2.0-14.5). Thirteen had ALL, one had myelodysplastic syndrome and three had solid tumours. Following vaccination, the VZV-specific stimulation index (SI) increased from 1.7 (0.9-2.9) to (5.9-36.0) (P < 0.001). Similarly, SI to phytohaemagglutinin mitogen increased from 1136 (499-1930) to 1714 (848-2518) (P = 0.028). were also significant increases in CD4+ cells and CD4 : CD8 ratio well as a reduction in CD16/56+ cells in peripheral blood Seroconversion rate to VZV was 19% after one dose and increased to 94% after the second dose of VZV vaccine. Serum VZV-specific IgG concentrations also increased significantly following two doses when compared with one dose of VZV vaccine (P = 0.0004). One subject developed possibly vaccine-related chickenpox with self-limiting hepatitis at 5 wk following vaccination. None of the patients developed herpes-zoster at a median (range) follow-up of 27.5 months (24.0-30.0). Conclusions: Non-immune cancer children can be effectively vaccinated against chickenpox at the defined period. However, the of chickenpox vaccine in these immunosuppressed children needs to further studied.