Emerg Infect Dis

Among patients with coronavirus disease (COVID-19), IgM levels increased early after symptom onset for those with mild and severe disease, but IgG levels increased early only in those with severe disease. A similar pattern was observed in a separate serosurveillance cohort. Mild COVID-19 should be investigated separately from severe COVID-19.2020R01 AG054046/AG/NIA NIH HHS/United StatesT32 HL116271/HL/NHLBI NIH HHS/United States32857691PMC7706962877