To understand how frequently stem helix–specific Abs are elicited, we analyzed plasma samples from prepandemic, COVID-19–convalescent, and COVID-19–vaccinated individuals to determine IgG binding titers to the SARS-CoV-2–SARS-CoV (SARS-CoV/-2), OC43, MERS-CoV, HKU1, HKU4, and HKU5 stem helix peptides (Fig. 5A and fig. The gene discussed is DDX41; the disease is COVID-19.