Blood tests to detect antibodies against SARS-CoV-2, the virus that causes COVID-19, are an important tool for diagnosing the disease, developing potential treatments, and checking vaccine efficacy. Although such tests are available, we have very little understanding on how different antibodies interact with virus antigens. Scientists set out to assess various antigen-specific antibodies and determined which of them had the strongest neutralizing activity against SARS-CoV-2.