SARS2 and infection: To confirm the single-round infection of IBIS, parental VeroE6 cells and Vero A9B21 cells were either mock infected, or infected with the IBIS vaccine, a defective SARS‐CoV‐2 with modified envelope (SARS2-mE), or wildtype SARS-CoV-2 virus at a multiplicity of infection (MOI) 0.1 for 24 h (Fig. 1b).