Look at the following article at The Scientist:
What Do Antibody Tests For SARS-CoV-2 Tell Us About Immunity
Studies from serum samples could transform our understanding of the spread of COVID-19, but what antibodies alone say about immunity is not yet clear.
It’s months into the coronavirus pandemic and public health officials still don’t know how many people have actually contracted the culprit, SARS-CoV-2. In many countries testing capacity has lagged behind the spread of the virus. Large numbers of people have developed COVID-19 symptoms but have not been tested, and the vast majority of people who had the virus but never developed symptoms and therefore were not tested, are not reflected in official statistics.
Federal and state governments, companies, and research groups are now racing to develop antibody tests to shine a light on the true spread of SARS-CoV-2. While PCR tests currently used to diagnose cases detect the virus’s genetic material, antibody tests can screen for virus-attacking antibodies that are formed shortly after an initial infection. Those antibodies usually linger in the blood long after the virus is gone. One such antibody, or serological, test was given emergency use authorization by the Food and Drug Administration in early April, and a number of other groups are making more tests, and in some cases even deploying them.
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