PALO ALTO, Calif. - Stanford University released results Friday of the nation's first large-scale community study of antibodies for the new coronavirus SARS-CoV2.
The study tested 3,330 Santa Clara County residents for COVID-19 antibodies by using finger-prick blood samples taken April 3rd and 4th.
The study was published in an online journal and the study's data suggests tens of thousands of people in the county with infections, compared to the official tally that shows less than two-thousand confirmed cases.
"This implies the coronavirus epidemic is substantially more widespread that the extent implied by the number of cases identified to date," said Dr. Eran Bendavid, a Stanford Associate Professor of Medicine who was a lead on the study.
Participants included both adults and children who were recruited through Facebook ads to get a range of zip codes, gender and race.
Based on the number of participants who had positive coronavirus tests, researchers estimate between 48,000 and 81,000 people in Santa Clara County were infected by the virus as of early April.
That's a huge difference from 1,870 confirmed coronavirus cases Santa Clara County Public Health Department says have been reported so far.
That could indicate the coronavirus case fatality rate is lower.
"It is absolutely less lethal. At the same time, it's quite a lethal virus and there's still people very sick from it and dying every day," says Dr. Jay Bhattacharya, a Stanford Professor of Medicine who was a co-author of the study.
The blood tests checked for the presence two types of antibodies called IgM and IgG.
The researchers say their data estimates 2.5 to 4.2% of people in the county have antibodies, but that is far short of the 60-70% needed for herd immunity.
Also, no one knows yet how many antibodies are needed to protect against reinfection.
"The antibodies we are testing for are evidence of prior infection, not necessarily evidence of immunity and that's something which is being scientifically debated," said Dr. Bhattacharya.
Also unknown is when the participants who tested positive became infected.
'We don't have enough information to be able to say exactly when the infection started from the antibodies themselves," said Dr. Bhattacharya, "As best as I can tell, the science of that is still being clarified."
The Stanford study's results are preliminary and have not been peer-reviewed yet.
The Stanford researchers say there is a great need for scientists elsewhere to conduct testing in other regions.
The Stanford team is working on another study with Major League Baseball to take samples from 27 teams' employees to look at national spread.
Other studies at Stanford, U.C. Berkeley and Los Angeles are set to begin soon.