Large-scale antibody testing has already been performed in parts of the U.S. and Europe. For example, in Chelsea, Mass., 64 out of 200 people in the downtown area tested positive for COVID-19 exposure using antibody testing. Other areas have also reported high prevalence of antibody response to SARS-CoV-2, including 25 per cent in New York City, approximately 2.8 per cent in Santa Clara County, Calif., and 14 per cent in Gangelt, Germany.
Several companies have begun producing antibody testing kits, some of which have received regulatory approval. Currently, Health Canada has approved only one antibody test. The U.S. Food and Drug Administration has issued emergency use authorization for 12 tests, including a combination of lab-based and point-of-care tests, while 200 other devices are awaiting approval.
While these data imply that significantly more people have been exposed to or infected with SARS-CoV-2 than have been diagnosed using nucleic acid-based tests, these antibody-positive people may not be immune to SARS-CoV-2.