Summary: Since its outbreak in December 2019, the coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), led to an enormous rise in scientific response with an excess of COVID-19-related studies on the pathogenesis and potential therapeutic approaches. Solid organ transplant (SOT) recipients are a heterogeneous population with long-lasting immunosuppression as a joining element. Preliminary data suggest that although SARS-CoV-2 vaccines are safe in SOT recipients (with similar rate of adverse events than in the general population), the antibody responses are decreased in this population. mRNA- SARS-CoV-2 vaccine elicits either cellular or humoral response in almost two thirds of KTRs. in a population with a reduced antibody response information about the T cell response should be part of the assessment and furthermore it could be part of an individualized management strategy. Risk factors for poor vaccine immunogenicity include older age, shorter time from transplantation, use of mycophenolate and belatacept, and worse allograft function.