The researchers performed a high throughput Surface Plasmon Resonance imaging (SPRi) assay to measure the level of IgG, IgM and IgA antibodies that bind to the SARS-CoV-2 spike protein receptor binding domain (RBD). Samples were collected from 53 unique COVID-19 patients and controls were collected from healthy pregnant women. According to the analysis, the results from IgG SPR correlated with the results from S1 domain ELISA and the total Ig SPR results were also similar to the ECLIA total Ig results, showing the efficiency of the technique. Additionally, the affinity equilibrium constant (KD) correlated with the off-rate (Kd), making the off-rate parameter a good ranker of binding strength for SARS-CoV-2 antigens and simplifying the high throughput test. Through this analysis, the researchers concluded that low concentrations of high avidity anti-RBD antibodies can effectively neutralize SARS-CoV-2 and the SPRi can be used to adequately determine the neutralizing effects of IgG after vaccination.