The patients of pediatric haemato-oncology have a higher risk for novel H1N1 influenza infection than general population, and they are strongly recommended to receive novel H1N1 vaccination. However, there is no previous data to answer how the efficacy and effectiveness of novel H1N1 vaccination is in patients of pediatric haemato-oncology. This study is designed to investigate the antibodies titers before and after the novel H1N1 influenza vaccination in these patients. Titer of H1N1 influenza virus antibodies will be determined by hemagglutinin inhibition assay (HAI). A HAI titer with a 4-fold rise or greater is defined as seroconversion. Study subjects with seroconversion are regarded as responsiveness to the vaccination. Meanwhile, if the patient presents influenza-like symptoms, we will perform throat swab or nasal swab for influenza rapid test, viral isolation, and novel H1N1 influenza PCR to confirm the diagnosis. After the study, we will be able to know whether or not current novel H1N1 influenza vaccination schedule is adequate and efficient for pediatric haemato-oncology patients.