Abstract: The disclosure provides method, kits, and devices for detecting and/or assessing neutralizing antibodies in a sample, e.g. a biological sample. The detection comprises contacting the sample to an antigen of a virus of interest, and detecting the binding of the one or more IgG3 antibodies to the antigen. The presence of IgG3 antibodies that specifically bind the virus antigen indicates neutralizing antibodies against the virus. The detection protocol can be implemented in a variety of configurations and formats, including ELISA-type and lateral flow formats. The method can be used to assess, e.g., a subject's relative immunity or infection status regarding a particular virus, such as SARS-CoV-2.