Antibody testing likely undercounts the number of people who have had COVID-19: More than 25% of infected health care workers had NO signs of it in their blood work 60 days later

CDC researchers found that 6% of more than 3,000 health care workers they tested had antibodies to coronavirus. Within 60 days, when they were retested 28% of the health care workers had antibody levels so low that they could no longer be detected. Researchers warn this suggests that using antibody testing likely undercounts how many people have had COVID-19 and that plasma has a short shelf life