To exclude healthy controls with a previous SARS-CoV-2 infection, we tested the subjects for SARS-CoV-2-specific IgG antibodies by performing the Euroimmun anti-SARS-CoV-2 ELISA (IgG) (EUROIMMUN, Lübeck, Germany) (Table S2). An IgG ratio of > 2.5 was considered a positive test, a ratio between 0.8 and 2.5 was considered an intermediate result and a ratio < 0.8 was considered a negative test (28 (link)).
Free full text: Click here