The Pfizer/BioNTech BNT162b2 vaccine has been approved for the prevention of coronavirus 2 severe acute respiratory syndrome (SARS-CoV-2) and is recommended for immunosuppressed patients. However, its efficacy and safety in patients undergoing immunological cell therapy have not been well documented. In this study, we evaluated the efficacy and safety of the BNT162b2 vaccine in patients who underwent hematopoietic cell transplantation (HCT) and chimeric antigen receptor (CAR)-T therapy. We prospectively followed 79 vaccinated patients who were actively treated at Tel Aviv Sourasky Medical Center and monitored the safety profile and humoral immune response to the vaccine.

Overall, the vaccine was well tolerated and all side effects resolved within a few days, except for secondary graft rejection, which is still under investigation. We observed that only 36% of patients who received CAR-T therapy developed a humoral antibody response compared to 81% of patients who underwent allogenic HCT. In addition, patients with B-cell aplasia and those who received the vaccine shortly after cell infusion were less likely to develop antibodies. Taken together, these data demonstrate that the humoral response to the BNT162b2 vaccine is significantly altered in patients receiving CAR-T, as opposed to those after allogenic HCT who had a good response.