Immunogenicity of trivalent influenza vaccine in children with acute lymphoblastic leukemia during maintenance...

The aim of this study was to assess the immune response of children with acute lymphoblastic leukemia (ALL) to influenza vaccine and to compare it with healthy controls.

Thirty-two children aged 1-18 years with ALL on maintenance therapy and 30 healthy sibling controls were enrolled in the study. All children were vaccinated with trivalent inactivated influenza vaccine. Hemagglutinin-inhibition (HI) antibody titers were determined in sera of both patient and control groups just before and 4 weeks after vaccination. The ability of each group to mount a protective (> or =40) and/or fourfold titer was measured.

The protective response for virus subunits among patients and healthy controls were 43.4% versus 88% for H1N1 (P = 0.04), 63.3% versus 80% for H3N2 antigens (P = 0.06), and 26% versus 73% for B antigen (P = 0.001). Responses for H1N1 and B subunits were significantly lower in patients than controls. In the patient group, the significant response to each virus was demonstrated in the analysis of pre- and post-vaccination geometric mean titer (GMT) (P = 0.001). The percentage of patients and controls with fourfold increase in HI titers were 56.2% versus 80% for H1N1 (P = 0.04), 40.6% versus 53.3% for H3N2 (P = 0.31), and 59.4% versus 83.3% for B (P = 0.038). Immune responses for H1N1 and B subunits were significantly lower in patients than controls.

Influenza vaccine is tolerated well in ALL patients with acceptable but limited immune response compared to healthy controls. These findings support the recommendation for annual influenza vaccination in children with ALL.