title: Does vaccine dose predict response to the monovalent pandemic H1N1 influenza a vaccine in children with acute lymphoblastic leukemia? A single-centre study.
abstract: BACKGROUND
  Vaccination against influenza is an important strategy in preventing severe infection among children with acute lymphoblastic leukemia (ALL). Successful vaccination depends on both vaccine and host-related factors. We conducted a study on factors predicting the immunogenicity of the monovalent pandemic H1N1 (pH1N1) influenza A vaccine in children with ALL.
  
  
  METHODS
  Children with ALL in our hospital were recruited and received two doses of the inactivated split-virion AS03-adjuvanted vaccine. The serological response was measured before each vaccine dose (Day 0 and 28) and 3 months after the second dose. Antibody titres were measured using a hemagglutination-inhibition assay. Seroconversion was defined as a ≥fourfold increase in antibody titre and a post-vaccination titre ≥1:40.
  
  
  RESULTS
  Pre and post-vaccination titres were available from 45 children with ALL after one dose of the vaccine and 39 children after two doses. The seroconversion rate was 11.1% after one dose and 25.6% after the second dose. Univariate analysis demonstrated a significantly higher (P = 0.01) seroconversion rate among children who received the adult dose (0.5 ml) of the vaccine and a trend towards increased seroconversion (P = 0.07) by multivariate analysis. Factors including age, gender, lymphocyte count, treatment phase and regimen did not significantly affect the seroconversion rate. Children who received the adult dose demonstrated a significantly greater magnitude of serological response after both one dose (P = 0.04) and two doses (P = 0.001).
  
  
  CONCLUSIONS
  These data suggest that the immunogenicity of the pH1N1 vaccine among children with ALL is improved by repeated and adult doses of the vaccine.
authors.affiliation: Department of Paediatric Infectious Diseases and Immunology, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland. tronanleahy@hotmail.com
authors.forename: T Ronan
authors.initials: TR
authors.lastname: Leahy
authors.forename: Owen P
authors.initials: OP
authors.lastname: Smith
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Bacon
authors.forename: Lorna
authors.initials: L
authors.lastname: Storey
authors.forename: Paul
authors.initials: P
authors.lastname: Lynam
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Gavin
authors.forename: Karina M
authors.initials: KM
authors.lastname: Butler
authors.forename: Aengus S
authors.initials: AS
authors.lastname: O'Marcaigh
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006801:Humans; D007117:Immunization, Secondary; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D058873:Pandemics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma
chemical_list: D007252:Influenza Vaccines
keywords: acute lymphoblastic leukemia; immunogenicity; influenza A; pandemic H1N1; vaccine