To determine whether the remaining antibodies (Abs) that were induced after the initial infection directly contribute to the protection against reinfection, one young CM (#012) was intratracheally rechallenged with the same dose of SARS-CoV-2 as that used for the initial infection (1 × 106 TCID50) at 112 d p.i., when the level of the receptor binding domain (RBD) of SARS-CoV-2–specific Ab titer and neutralizing Ab (nAb) activity had decreased to the levels before infection. Here, DDX41 is linked to infection.