Studies on the humoral immune response to hemagglutinin of influenza vaccine in children with acute lymphoblastic leukemia after chemotherapy treatment

Purpose The aim of this study was to assess the humoral response to influenza vaccine in children with acute lymphoblastic leukemia after completed chemotherapy treatment. Patients and Methods In the epidemic season 1993/ 94 and 1996/97 twenty-two patients were vaccinated against influenza. In 10 of them chemotherapy had been completed before 1991 (A) and in 12 patients it had been completed after 1991 (B). The second group consisted of 20 patients vaccinated for the first time in the 1996/97 season who were divided into subgroups A and B. All patients received single 0.5 ml dose of subunit vaccine ('FluShield', Wyeth in 1993/94; 'Influvac',Solvay Duphar in 1996/97). Humoral response was determined before vaccination, 3 weeks and 6 months after vaccination by the hemagglutinin inhibition test (HI). Results were compared with those of healthy non-vaccinated children and a statistical analysis was performed using the Mann-Whitney test and Wilcoxan test. Results Three weeks after vaccination a significant increase in antibody levels was found for all tested antigens when compared with the pre-vaccination results. After 6 months a further increase of antibody titers was observed. After vaccination protection rates ranged from 33.3% to 100%. In 1993/94 response rates ranged from 25% to 60%, while after the second immunization these values increased to 41.7-100%. In children vaccinated for the first time in 1996/97 response indexes ranged from 40% to 100%. There were no significant differences in humoral response between patients from group A and those from group B. The highest antibody titers were recorded for hemagglutinin HE and H3, while the lowest levels were found for hemagglutinin H1. Conclusions The results of this study clearly indicate the immunogenicity of influenza vaccine in children with acute lymphoblastic leukemia and show a significant humoral response to all hemagglutinins included in the vaccines regardless of the date when chemotherapy had been completed.