Does vaccine dose predict response to the monovalent pandemic H1N1 influenza a vaccine in children with acute lymphoblastic leukemia? A single-centre study

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. Pediatr Blood Cancer 2013;60:1656–1661. © 2013 Wiley Periodicals, Inc.