2.5 Neutralization assay
The pseudo-neutralization assay was performed by using the SARS-CoV2 Neutralization Antibody Elisa Kit (Invitrogen) as per manufacturers protocol. In brief, plasma samples were diluted 1:50 and added to wells coated with SARS-CoV2 RBD (Receptor Binding Domain) antigen followed by incubation and addition of Biotin conjugate. After required incubation period Streptavidin-HRP conjugate was added followed by addition of Substrate solution (TMB) and Stop solution after successive incubation periods. The plate was read on iMark microplate absorbance reader (Bio-Rad) using 450nm wavelength. Neutralization % was calculated by the following formula:
Neutralization (%) = 1- (Absorbance of unknown sample/Absorbance of negative control) × 100
> 20% = Positive
< 20% = Negative