SARS-CoV-2 IgG and IgA ELISA
Serum IgG or IgA antibodies against SARS-CoV-2 were determined in serum samples by enzyme linked immunosorbent assay ELISA according to the manufacturer (agile SARS-CoV-2 IgG ELISA, Virion/Serion, Wuerzburg, Germany) given a sensitivity of 96.2% and a specificity of 100% (Stromer, Rose et al. 2020). IgG and IgA concentrations were positive for values ≥15U/mL and 14U/mL, respectively. Individuals with IgG concentrations below 15U/mL were considered as non-responders and analyzed independently. IgA concentrations were determined in IgG positive samples only.