Longevity of IgG antibodies:
In one 65 year old male patient with a mild course of disease the neutralizing antibody titer dropped from 1:32 at T1 to <1:8 at T5.
Two patients showed an increase in neutralizing antibodies over the sample period. In both patients, the first blood sample showed weak or moderate neutralizing ability with titers of 1:4 and 1:8, which increased to titers of 1:32 and 1:64, respectively. The courses of disease in these cases were mild and severe, respectively.
In 83.9% of the patients, the neutralizing antibody titers against SARS-CoV-2 stayed constant and did not change more than two dilution steps or more than 50% change of optic density in CLIA IgG.
Two patients were negative in the CLIA IgG assay but showed weak neutralizing activities with antibody titers of 1:4.