New antibody tests offer a better snapshot of coronavirus immunity

Quantitative antibody testing could also help with treatments involving convalescent plasma

A new crop of Covid-19 antibody tests measures the level of protection someone has built up against the deadly virus and may help determine which vaccines are most effective.
 

Siemens Healthineers AG is the first big company to gain US Food and Drug Administration clearance for a test that gauges the concentration of long-lasting antibodies flowing through a person’s blood. Swiss giant Roche Holding AG is following up with its own version.
 

Antibodies are markers of infection, and testing for them helps health officials see how widely the virus has spread. Until now, most tests could tell only whether they’re