Influenza Specific Immunity After Vaccination in Recipients of Haematopoietic Stem Cell Transplantation Compared to Healthy Controls

This study is looking at whether children who have had a bone marrow transplant produce protective antibodies after the flu vaccine. We will compare this to healthy children, and also look at how many children get the flu despite being vaccinated. Who is it for? You or your child may be eligible to join this study if you/they are aged between 6 months to 18 years, and have undergone haematopoietic stem cell transplant 6 months to 2 years ago. Study details Bone marrow transplant (BMT) patients have significant problems with their immune system. The rate of problems caused by the flu (influenza) is particularly high in these patients. Vaccination is the main way to prevent the flu and the problems it causes. Vaccination of children and adolescents may not only protect the children themselves, but may also significantly decrease the rate of transmission and consequently, the knock-on effects in the general population. There are many studies in adults that have looked at the immune response of the flu vaccine in patients post transplant. Response rates are poor and whilst the response improves over time with recovery of their immune system, it rarely reaches that of healthy controls. The rates reported are between 9-40%. The studies that have been done are small. There are limitations to these studies and importantly, there is minimal amount of data for children. To our knowledge, there have been no studies conducted looking at the immune response to the flu vaccine in children alone. In this study all participants will receive the influenza vaccine as per immunisation guidelines. After each vaccine dose (1-2 doses may be administered), participants will undergo a blood test to evaluate influenza specific antibody levels. Participants will also be monitored from enrolment to the end of the influenza season (end of November of enrolment year) in order to identify frequency and severity of influenza infection.