As the country shifts its focus to reopening schools and businesses, there are high expectations on researchers in California conducting the first few rounds of antibody testing.

Scientists at the University of Southern California (USC), Stanford University and University of California, Los Angeles (UCLA), began working with local public health departments to conduct large-scale antibody testing earlier in April. Now, preliminary results from the first large-scale community test of 3,300 people in Santa Clara County has found that 2.5 to 4.2 percent of those tested were positive for antibodies, according to a report by ABC.

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Generally, if a patient tests positive for a coronavirus antibody, it means they've had it in their bloodstream, either by contracting the disease or through a vaccine. Since there are no COVID-19 vaccines currently approved for public use, the results suggest that anywhere between 48,000 and 81,000 people in the county of 2 million have had the coronavirus, although the official number was just 1,000 when antibody testing first began.

“Our findings suggest that there is somewhere between 50- and 80-fold more infections in our county than what’s known by the number of cases than are reported by our department of public health," Eran Bendavid, doctor and associate professor of medicine at Stanford University who led the study, told ABC.

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Still, the results collected from volunteers are not necessarily representative of the U.S. population as a whole. There are also some concerns about the quality of the serology tests, which are not standardized. While the Food and Drug Administration (FDA) has authorized a few tests under an Emergency Use Authorization, none of these have been fully reviewed and authorized.

The Stanford test, developed by the university, takes two to three days to provide results and looks for antibodies to the virus in plasma — the liquid in blood — to provide information about a person’s immune response to an infection. Other tests, such as the one being used by USC researchers in Los Angeles County, provide results more quickly, but only reveal whether or not antibodies are present in the bloodstream.

The USC test, which is being conducted in Los Angeles County, is manufactured by Premier Biotech, and has tested blood from COVID-19-positive patients with a 90 to 95 percent accuracy rate, according to Neeraj Sood, the lead investigator of the study. But there are still many questions left unanswered.

“COVID-19 is a new disease, so we don’t know whether antibodies give 100% immunity or not. We don’t know how long this immunity lasts. That’s still being debated. Most people think that the risk of reinfection for someone with antibodies is low. Basically, what we’re saying is if you have antibodies, you’re probably better off than someone who doesn’t have antibodies,” Sood said in a USC release.

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