Based on its safety and immune-stimulating features, we hypothesized that the heat-inactivated VACV or MVA could act as vaccine adjuvant because: (i) it mimics natural infection except for lost replication capacity; (ii) it induces type I IFN production in cDCs via the cGAS/STING pathway and in pDCs via the TLR9/TLR7/MyD88 pathway31,32; (iii) immunosuppressive genes antagonizing type I IFN production/signaling encoded by the MVA genome were not expressed in heat-inactivated MVA (heat-iMVA) infected cells. This evidence concerns the gene STING1 and infection.