The IgG anti-RBD antibody and IFN-γ responses against the original and variant S proteins at T1 were compared between 64 SARS-CoV-2-uninfected participants (33 without and 31 with SARS-CoV-2 breakthrough infections at T3) and 18 SARS-CoV-2-infected participants (SARS-CoV-2 breakthrough infections identified at T2). This evidence concerns the gene IFNG and infection.