Fig. 3

SARS-CoV-2 virus challenge test on young and old mice. A and B ssAAV5-RBD-plus significantly increased NAs in young and old BALB/c mice; C and D RBD-plus provided excellent protection in the lungs, showing a decrease in viral titre of more than 4.0 Log copies/g in lung tissues of vaccinated young and old mice; E and F After 3 and 5 days of viral inoculation, titers of infectious virus in the nose dropped nearly 1.0 Log copies/g in young and old mice.