“Immunity Passports” are being touted as one way to reopen the economy. These passports would be administered to people who test positive for having had the coronavirus. Scientists worldwide have developed dozens of these tests, hoping to distribute them throughout the world. However, even highly accurate tests will run into a problem.

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   SARS-CoV-2 (COVID-19) by the numbers.

   
   
   
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   Large-Scale Antibody Test Suggests As Many As 80,000 Santa Clara County Residents Have Already Had COVID-19

   
   
   
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   Antibody Test, Seen as Key to Reopening Country, Does Not Yet Deliver