IMMUNOGENICITY OF SUBUNIT TRIVALENT INFLUENZA VACCINE IN CHILDREN WITH ACUTE LYMPHOBLASTIC-LEUKEMIA

Background. The aim of this study was to assess humoral response to in fluenza vaccine in children with acute lymphoblastic leukemia. Methods . Studies were performed in 25 patients previously vaccinated against influenza (Group A) and in 20 children who had never been immunized be fore (Group B). In Autumn, 1996, they were vaccinated with subunit tri valent influenza vaccine containing 15 mu g of hemagglutinin of A/Sing apore/6/86, A/Wuhan/359/95 and B/Beijing/184/93. Antihemagglutinin (HI ) and antineuraminidase antibody titers were determined before immuniz ation and 3 weeks and 6 months after vaccination by the hemagglutinin inhibition test and the neuraminidase inhibition test. All results wer e presented as the geometric mean titer of antibodies, mean fold incre ase of antibody titer, protection rate and response rate. Results. In Group A mean fold increase of HI antibodies ranged from 17.2 to 26.7 t hree weeks after vaccination and from 22.1 to 38.2 six months after va ccination, while in Group B it ranged from 15.7 to 22.6 and from 30.3 to 39.3, respectively. In the case of neuraminidase, mean fold increas es for Group A varied fi om 9.2 to 13.2 three weeks after immunization and from 15.6 to 21.1 sis months after vaccination, whereas for Group B they varied from 5.5 to 8.3 and from 14.4 to 23.4, respectively, Si s months after vaccination the proportion of subjects with HI antibodi es greater than or equal to 1:40, as well as those with at least 4-fol d increase of BI antibody titers, ranged from 68 to 100% in Group A an d from 90 to 100% in Group B. No vaccinated child was infected with th e influenza virus; the vaccine was well-tolerated and did not cause an y adverse reactions, Conclusions. The results obtained in this study i ndicate that influenza vaccine is immunogenic in patients with acute l ymphoblastic leukemia, despite their serious disease.