CD8A and COVID-19: That LD and HD groups had similar CD8+ CTL responses, serum antibody response is not considered a determining factor of efficacy for intranasal vaccination, and HD groups (52%) had much higher mucosal antibody responses than LD group (21%) suggests that the 67.8% rVE of HD CVXGA1 over LD CVXGA1 may be attributed to the higher levels of mucosal antibody responses in HD CVXGA1 recipients; i.e., mucosal antibody response may be a correlate of protection for an intranasal COVID-19 vaccine.