KRT18 and infection: Since infection with rSARS-CoV-2 Δ3a/Δ7b was not lethal in K18 hACE2 transgenic mice (Fig. 3E and F), but it induced robust humoral (Fig. 3G) and cellular (Fig. 3H) immunity, we hypothesized that the K18 hACE2 transgenic mice vaccinated with rSARS-CoV-2 Δ3a/Δ7b would survive a lethal challenge with wild-type virus, confirming the feasibility of rSARS-CoV-2 Δ3a/Δ7b as an LAV strategy.