Preexisting antibodies has been shown to be able to shape the recall immune responses upon influenza infection and vaccination.6 And the concern about how the preexisting immunities may influence the effect of a SARS-CoV-2 vaccine has also attracted lots of attention.33 To investigate the impact of the preexisting P144 antibodies on the immunogenicity of a candidate DNA vaccine, 18 BALB/c mice were divided into 3 groups according to their levels of preexisting S2 binding antibodies and immunized with a DNA vaccine encoding the full length of SARS-CoV-2 S protein (Figure 4a and 4b). The gene discussed is PROS1; the disease is influenza.