Wang Y, Zhang L, Sang L, et al. - The causative agent for coronavirus 2019 (COVID-19) pneumonia is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Researchers sought to report on the kinetics, tissue distribution, cross-reactivity, and neutralization antibody response in patients with COVID-19. In this study, they enrolled two groups of patients with RT-PCR–confirmed COVID-19: 12 severely ill patients in intensive care units who required mechanical ventilation and 11 mildly ill patients in isolation wards. Assessment of serial clinical samples revealed viral shedding in a variety of tissues for 20–40 days after onset of disease in most of the severely ill patients (8/12, 66.7%), while viral shedding was restricted to the respiratory tract in the majority of mildly ill patients, with no detectable virus RNA 10 days after onset (9/11, 81.8%). Relative to the severe group, mildly ill patients showed significantly lower IgM response. Most patients in both the groups showed IgG responses at 9 days after onset; these remained at a high level throughout the study. Patients with COVID-19 but not patients with MERS had antibodies cross-reactive to SARS-CoV and SARS-CoV-2. Both severely and mildly ill patients showed high levels of neutralizing antibodies after about 10 days of onset, which were higher in the severe group. Sera from patients with COVID-19, but not from convalescent patients with SARS or Middle East respiratory syndrome (MERS), inhibited SARS-CoV-2 entry. In patients’ plasma, anti–SARS-CoV-2 S and N IgG levels exhibited a moderate association with neutralization titers. This study thereby yields further information concerning the immune response in humans after SARS-CoV-2 infection.