Abstract
Allogeneic hematopoietic stem cell transplant (AHSCT) recipients are at a risk of developing immune-mediated tissue damage from activation of the donor's immunocompetent T cells by the recipient's normally expressed antigens, a phenomenon called graft-versus-host disease (GVHD). With the emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), new vaccines have been developed to prevent morbidity and mortality, including the highly vulnerable hematologic malignancy patients after undergoing AHSCT. The early pathophysiologic events in GVHD include priming the donor T cells with molecules that are endogenous or pathogenic. In this case series, we present two cases of AHSCT recipients in which the SARS-CoV-2 vaccination series proceeded the development of GVHD manifesting with oral mucosal symptoms and derangement in the liver function tests. Our experience raises the question if any of the vaccine components serve as a molecular trigger for GVHD, making the current SARS-CoV-2 vaccines a risk factor for activating the immune system and developing GVHD.