Real-life data on anti-SARS-CoV-2-S1-IgG titers (n = 192) and IFN-γ release (n = 110) of allo-HCT recipients were obtained using commercially available, validated assays after vaccination with either mRNA (ComirnatyTM, Pfizer-BioNTechTM, NY, US and Mainz, Germany or SpikevaxTM, ModernaTM, Cambridge, Massachusetts, US) or vector-based vaccines (VaxzevriaTM,AstraZenecaTM, Cambridge, UK or Janssen COVID-19 vaccineTMJohnson/Johnson, New Brunswick, New Jersey, US), or after a heterologous protocol (vector/mRNA). This evidence concerns the gene IFNG and COVID-19.