Pandemic Influenza Vaccine in Organ Transplantation (PIVOT Trial)

This randomized, placebo-controlled, double-blind, single-centre trial will evaluate the immunogenicity and safety of a two-dose regimen of the AS03-adjuvanted inactivated H5N1 vaccine (AREPANRIX™ H5N1, GSK) in adult organ transplant recipients. A total of 120 stable outpatient organ transplant recipients at the University Health Network (Toronto, Canada) will be enrolled and randomized 1:1 to receive two doses of H5N1 vaccine or placebo (0.9% saline) administered intramuscularly 3 weeks apart. Blood samples collected at baseline (V0), 3 weeks (V1), and 6 weeks (V2) will be analyzed for serologic responses using hemagglutination inhibition (HAI) assays against vaccine and circulating H5N1 strains. In a subset of 60 participants (30 per arm), peripheral blood mononuclear cells will be obtained at each time point to assess cell-mediated immunity, including H5-specific CD4+ and CD8+ T-cell cytokine responses and B-cell immunity. Participants will be monitored for local and systemic adverse events for 7 days following each dose and followed for 6 months for any adverse events, including rejection, influenza-like illness, and laboratory-confirmed influenza. Long-term immunogenicity will also be assessed at 6 months in vaccine recipients.