As the levels of S RBD-specific IgM, IgA, and IgG antibodies significantly increased in patients after their recoveries from COVID-19, and as only the IgA and IgG antibodies were predominantly observed after vaccination, we analyzed the correlations of the different classes of antibodies against the Wuhan strains and three SARS-CoV-2 variants. The gene discussed is CD40LG; the disease is COVID-19.