CD4+ T-cell count to predict the response to new H1N1 vaccination in pediatric patients with cancer.

Abstract

9087 Background: The efficacy of vaccination in (pediatric) cancer patients is still a topic of debate. We aimed to study the immunologic determinants of influenza vaccination response in pediatric cancer patients. Methods: We measured the vaccination response to the new swine-origin influenza A H1N1 in relation to lymphocyte subpopulations in 33 pediatric cancer patients, being treated with chemotherapy or within 6 months after the end of chemotherapy. All patients were vaccinated twice with an intramuscular injection with inactivated split-virion preparation of the A/California/07/2009(H1N1)v like strain (X-179A), which contained 7.5μg of hemagglutinin per dose of 0.5 ml. A protective response was defined as achieving a HI antibody titer ≥ 1:40 following vaccination. Results: From the 33 included patients, 19 (58%) had a protective immune response. We showed a significant relation between response on vaccination and levels of all of the different lymphocyte subpopulations (p<0.001 for the CD4+ T-cells and p=0.001 for total T-cells, CD8+ T-cells and B-cells). Patients with an absolute CD4+ T-cell count less than 200/mm3 did not have a protective vaccination response to new H1N1. Conclusions: Absolute CD4+ T-cell count predicts the response to influenza vaccination in pediatric cancer patients treated with chemotherapy. This finding has important implications for the establishment of a response on vaccination in pediatric cancer patients during treatment with chemotherapy.