Background: Children with cancer have an increased susceptibility to influenza infection. The objective of this study was to assess the immunogenicity of pandemic (H1N1) 2009 vaccine in children with cancer.
Methods: Children were recruited from the Royal Marsden Hospital, England, during November 2009. The vaccination schedule consisted of 2 doses of an AS03(B)-adjuvanted vaccine given at days 0 and 21. Serological analysis was performed on blood samples obtained at day 0 and day 42. The primary immunological end point was the seroconversion rate, which was defined as the proportion of subjects with an individual 4-fold increase in hemagglutination inhibition titer and a postvaccination hemagglutination inhibition titer ≥1:32.
Results: Fifty-four children with a median age of 6.3 years (range, 1.4-16.6 years) were vaccinated and had samples taken for serological analysis. Twenty-four (44.4%) of 54 children demonstrated seroconversion. Seroconversion rates were 33.3% (9 of 27) among children with acute lymphoblastic leukemia, 36.4% (4 of 11) among those with lymphoma or other leukemias, 66.7% (6 of 9) among those with brain tumors, and 71.4% (5 of 7) among those with other solid tumors. Seroconversion occurred in 4 (28.6%) of 14 children receiving acute lymphoblastic leukemia maintenance therapy. Univariate analysis showed significantly higher responses among children with solid tumors, compared with those with hematological malignancies (11 [68.8%] of 16 vs 13 [34.2%] of 38; P = .03), and among those not receiving treatment, compared with those receiving treatment (7 [87.5%] of 8 vs 17 [37.0%] of 46; P = .02). Multivariable analysis showed that age, cancer type, and lymphopenia did not influence seroconversion rates.
Conclusion: These data suggest that this AS03(B)-adjuvanted pandemic (H1N1) 2009 vaccine can induce limited but useful protective immune responses in children with cancer.