title: Varicella Vaccination of Children With Leukemia Without Interruption of Maintenance Therapy: A Danish Experience.
abstract: Varicella-zoster virus (VZV) can be fatal or cause severe complications in children with acute lymphoblastic leukemia (ALL). This analysis set out to investigate the morbidity and mortality of VZV vaccination without interruption of maintenance therapy in children with ALL.
  
  
  
  Files of 73 seronegative children with ALL were examined for data regarding VZV vaccination and infection, and long-term seroconversion was measured. Criteria before VZV vaccination were (1) seronegative, (2) in complete remission, (3) age ≥ 1.0 year, (4) lymphocyte count ≥ 0.6 × 10/L at time of vaccination and (5) receiving maintenance therapy.
  
  
  
  Forty-five children were vaccinated. No child died or experienced serious adverse events due to VZV vaccination. Nine children developed late chickenpox despite vaccination. Long-term protection was found in 86% of children not receiving acyclovir and 78% of the entire population. Long-term seroconversion was found in 52% of the children. There were no severe cases of varicella infection. Acyclovir prophylaxis postvaccination was associated with an increased risk of late chickenpox [hazard ratio = 5.40 (1.43, 20.41), P = 0.01]. In contrast, a vaccine-induced rash reduced the risk of late chickenpox [hazard ratio = 0.08 (0.01, 0.66), P = 0.02]. No child had interruption of maintenance therapy at the time of vaccination, but 33% experienced discontinuation of therapy due to vaccine-induced rash. Dexamethasone was associated with an increased risk of vaccine-induced rash [hazard ratio = 2.9 (1.21, 6.90), P = 0.02].
  
  
  
  This analysis indicates that VZV vaccination is feasible and justified in seronegative children with ALL, in countries where VZV vaccination is not part of the national vaccination program.
authors.affiliation: From the *Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Denmark; †Great Ormond Street Hospital, London, England; ‡Section of Biostatistics, Institute of Public Health, University of Copenhagen, Denmark; and §Institute of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lotte Møller
authors.initials: LM
authors.lastname: Smedegaard
authors.forename: Anja
authors.initials: A
authors.lastname: Poulsen
authors.forename: Ines Ackerl
authors.initials: IA
authors.lastname: Kristensen
authors.forename: Susanne
authors.initials: S
authors.lastname: Rosthøj
authors.forename: Kjeld
authors.initials: K
authors.lastname: Schmiegelow
authors.forename: Ulrikka
authors.initials: U
authors.lastname: Nygaard
mesh_terms: D000293:Adolescent; D002644:Chickenpox / Q000517:prevention & control; D019433:Chickenpox Vaccine / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D003718:Denmark; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy*; D012189:Retrospective Studies; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D019433:Chickenpox Vaccine