We have investigated preexisting cross-reactive antibody levels to SARS-CoV-2, including immunoglobulin G (IgG) antibodies to the spike 1 (S1), S1 receptor-binding domain (S1-RBD), and nucleocapsid protein (NP) antigens, in prepandemic serum samples collected from children and adults, and compared these to the antibody levels in serum samples from convalescent COVID-19 patients. The gene discussed is PSMD1; the disease is COVID-19.