High vs. Standard Dose Flu Vaccine in Adult Stem Cell Transplant Recipients

Influenza virus is a serious pathogen in immunocompromised persons, especially hematopoietic stem cell transplant (HSCT) recipients. However, these individuals respond poorly to trivalent inactivated influenza vaccine (TIV). High-dose TIV (HD-TIV) has increased immunogenicity and efficacy in adults ≥65 years of age and is FDA licensed for this population, while quadrivalent inactivated influenza vaccine (QIV) is licensed for other groups. It is not known whether HD-TIV will be safe and immunogenic in severely immunocompromised persons. The standard measure of immunogenicity for TIV is the hemagglutination inhibition (HAI) titer. The central hypothesis of our proposal is that HD-TIV will be more immunogenic compared to standard dose QIV in adult HSCT recipients as evident by higher HAI antibody responses to influenza A antigens. The results of this study will fill a significant gap in knowledge regarding influenza vaccine responses in adult HSCT recipients and will guide vaccine recommendations in this vulnerable population.