"Coronavirus antibodies are generally not detectable until 14 days after symptoms began. “In most viral infections, specific antibodies can be detected for months to years following infection – and in many cases well into old age,” says Berger."
14 days to late...... To stop the spread you need to identify the virus well before that hence why "Antigen Tests" are so much more valuable in the fight against COVID 19 and are the sort after test.
SONA a Canadian company developing an Antigen test went from approx $40m valuation to over $800m valuation post announcement of the development of their test. This is just to show the value being put on these types of tests.
