Study of the immunogenicity of alternative schedules of influenza vaccination in hematopoietic stem cell transplant recipients

INTRODUCTION: Influenza is a potentially severe illness after hematopoietic stem cell transplantation (HSCT). Vaccination is the main prophylactic strategy, but the immune response is limited in the compromised host. Existing data support the recommendation of influenza vaccination after the 6th month of HSCT. OBJECTIVES: The study evaluated different schedules of influenza vaccination in HSCT. Recipient and/or their donors were randomized to receive influenza vaccine before transplant. The primary outcome was the comparison of serotype response between groups at baseline, 30 days and 6 months after transplantation. METHODS: A randomized, non-blind trial was conducted in patients undergoing HSCT and respective donors at Hospital das Clínicas, Universidade Federal de Minas Gerais /BH-MG and at Hospital Amaral Carvalho/Jaú-SP. Four groups of donor and recipient pairs received different influenza immunization at least 7 days before HSCT: group 1 no vaccination, group 2 donor received a single dose of influenza vaccine; group 3 recipients received a single dose of influenza vaccine and group 4 recipients and donor received influenza vaccine. Following transplantation, all study patients were immunized with influenza vaccine at 6 months. Donor serum samples were collected at baseline (pre transplantation) and in the day of transplantation. Recipients serum samples were taken at baseline, 30, 60, 100, 180 days after transplantation, and at least 2 weeks after 6-month vaccination. The hemagglutination inhibition assay (HIA) was performed to evaluate immune response. HI antibodies titers 1:40 were considered protective. Titers < 1:10 were considered negative. Antibody response (seroresponse) was defined as the appearance or 4-fold rise in HI antibody titers after vaccination. RESULTS: From August 2007 to February 2010 131 donor and recipient pairs were included in the study: 38 pairs in group 1, 44 in the group 2 , 40 in 3 group and 9 in group 4.There were no...