title: Immunogenicity of a two-dose regime of varicella vaccine in children with cancers.
abstract: OBJECTIVE
  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) in a span of 3 months. Patients with acute 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 patients 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 17.9 (5.9-36.0) (P < 0.001). Similarly, SI to phytohaemagglutinin mitogen increased from 1136 (499-1930) to 1714 (848-2518) (P = 0.028). There were also significant increases in CD4+ cells and CD4:CD8 ratio as well as a reduction in CD16/56+ cells in peripheral blood lymphocytes. 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 safety of chickenpox vaccine in these immunosuppressed children needs to be further studied.
authors.affiliation: Department of Paediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong SAR, China. leung2142@cuhk.edu.hk
authors.forename: Ting-Fan
authors.initials: TF
authors.lastname: Leung
authors.forename: Chi-Kong
authors.initials: CK
authors.lastname: Li
authors.forename: Emily C W
authors.initials: EC
authors.lastname: Hung
authors.forename: Paul K S
authors.initials: PK
authors.lastname: Chan
authors.forename: Chi-Wai
authors.initials: CW
authors.lastname: Mo
authors.forename: Raymond P O
authors.initials: RP
authors.lastname: Wong
authors.forename: Ki-Wai
authors.initials: KW
authors.lastname: Chik
mesh_terms: D000293:Adolescent; D000914:Antibodies, Viral / Q000096:biosynthesis; D002644:Chickenpox / Q000209:etiology / Q000517:prevention & control; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005334:Fever / Q000209:etiology; D014645:Herpesvirus 3, Human / Q000276:immunology; D006801:Humans; D007111:Immunity, Cellular; D007115:Immunization Schedule; D016867:Immunocompromised Host; D008213:Lymphocyte Activation; D008297:Male; D009369:Neoplasms / Q000276:immunology*; D012449:Safety; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D019433:Chickenpox Vaccine; D014613:Vaccines, Attenuated