ATLANTA—Antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the disease COVID-19, have been measured in self-collected blood samples from residents of metro Atlanta in a new study by Drs. Alexis Bretin, Jun Zou and Andrew Gewirtz in the Institute for Biomedical Sciences at Georgia State University.
The researchers performed quantitative serology tests, which are laboratory tests that look for the presence of antibodies or specific proteins made in response to infections in blood serum. The antibodies measured by the test indicate the degree to which people had an immune response to SARS-CoV-2, regardless of whether symptoms developed from the infection or the infection was asymptomatic.
The researchers used a quantitative lab-based ELISA test, allowing them to set cut-offs that provided high specificity, minimizing false positives. This also allowed them to optimize sensitivity, although their quantitative approach demonstrated some false negatives are inevitable to achieve high specificity.
The findings, published on the preprint website medRxiv, are preliminary and have not yet been published in a peer-reviewed journal. While researchers note a small sample size (142 subjects), they nonetheless report that 7.1 percent of their unbiasedly selected participants had antibodies to SARS-CoV-2.
“There are clearly many more people infected than have been confirmed by nucleic acid testing,” said Dr. Alexis Bretin, one of the primary authors of the study and a postdoctoral research associate in the Institute for Biomedical Sciences.
“Persons with antibodies to SARS-CoV-2, who’ve not suspected they’d been exposed to this virus, can readily be found in various Atlanta area neighborhoods,” said Dr. Andrew Gewirtz, senior author of the study and professor in the Institute for Biomedical Sciences.
“Yet, most of the SARS-CoV-2 antibody positive subjects we identified had antibody negative household members, suggesting that asymptomatic carriers may only be moderately contagious,” added Dr. Jun Zou, an assistant professor in the Institute for Biomedical Sciences.
In any case, Gewirtz notes the “results also indicate that the vast majority of people in metro Atlanta remain vulnerable to this virus.”
In addition, the results support the utility of serology surveillance in advising public policy, but caution against the notion of “immunity passports” for individuals based solely on measure of anti-SARS-CoV-2 antibodies.
Results from serology tests allow scientists to estimate how many people have been infected by viruses, though the U.S. Food and Drug Administration advises against using results from antibody testing as the sole basis to diagnose or exclude SARS-CoV-2 infection or to inform infection status. Negative results do not rule out SARS-CoV-2 infection. Positive results could be from past or present infection with non-SARS-CoV-2 strains.
This is preliminary research that has not been peer reviewed. The study results require further analysis and should not be considered conclusive or used to guide clinical decision-making.
Read the study here.