Abstract

Background: Patients with acute lymphoblastic leukemia (ALL) have high risk of severe influenza infection and vaccination is highly recommended. The immunogenicity and effectiveness of vaccination are lower than in healthy people. Aim: To evaluate the immune response induced by influenza vaccine in children with ALL and observe effectiveness. Method: Children with ALL in maintenance phase and healthy children were recruited. Blood samples were taken at vaccination day (D0) and at day 28 (D28). Humeral response was evaluated by hemaglutination inhibition test (HAI) against H1N1. Patients were followed up for one year, clinical data and influenza episodes were recorded. Results: 34 children with ALL and 9 healthy children were included. Concerning HAI on D28, 12/34 patients and 5/8 healthy children had titers >= 1/40, with seroprotection rates of 35 and 63% respectively. Seroprotected children were older than non-seroprotected ones. During follow-up, only 3 patients non seroprotected, presented influenza infection, without oxygen supplementation or critical care support. Discussion: Children with ALL had a lower seroprotection rate than healthy children. Nevertheless, none of the seroprotected children presented influenza infection, reinforcing the annual vaccination recommendation.