TKT and neoplasm: To further improve the tumor selectivity and antitumor efficacy of VACV, various modified approaches have been used, including deletions of viral virulence genes such as thymidine kinase (TK) and vaccinia growth factor (VGF), insertions of therapeutic genes such as granulocyte-macrophage colony-stimulating factor (GM-CSF), co-stimulating factors and bispecific T cell engagers (BiTEs), and insertions of TAA especially neoantigens, etc., which enhance the antitumor capacity of VACV.