Antibody response to influenza vaccine in children with severe and mild hemophilia

Purpose The aim of this study was to assess humoral response to influenza vaccination in children with severe and mild hemophilia. Patients and Methods The study group consisted of 26 children with severe hemophilia (group A) and 12 children with mild hemophilia (group B) vaccinated against influenza ('Influvac', Solvay Pharmaceuticals B.V.). Antibody response was measured before vaccination, 3 weeks and 6 months after vaccination by hemagglutinin inhibition test and neuraminidase inhibition test. Control groups consisted of 23 healthy non-vaccinated people (group C) and 16 healthy vaccinated subjects (group D). Results Three weeks after vaccination antihemagglutinin (HI) antibody titers increased from 2.2 to 5.2 times in group A and 2.8 to 6.0 times in group B. Six months after vaccination a further increase of HI antibodies was observed for antigens H1N1 and H3N2. HI antibody titers for B/Beijing/184/93 were lower 6 months after vaccination than after 3 weeks. The highest proportions of subjects protected were observed 6 months after vaccination and they ranged from 65.4% to 96.2% in group A and 83.3% to 100% in group B. Antineuraminidase (NI) antibody levels 3 weeks and 6 months after vaccination were higher than those observed at the beginning of the study. No statistically significant differences were found in HI and NI antibody titers between patients with severe hemophilia and those with mild hemophilia. Conclusions Results indicate significant immune response to influenza vaccine in children suffering from severe and mild hemophilia. No differences were found between these two groups of patients.