Researchers from the National Institutes of Health analyzed 3 million antibody test results, also known as serology tests, from five commercial labs and two health care data analytics companies between January and August of 2020.
The researchers found that people with positive antibody tests were only about one-tenth as likely as those who didn't have antibodies to test positive for the virus 90 days after their initial antibody test. After 90 days, a positive test likely represents a new infection rather than viral shedding from the original infection.
"The data from this study suggest that people who have a positive result from a commercial antibody test appear to have substantial immunity to SARS-CoV-2, which means they may be at lower risk for future infection," Dr. Lynne Penberthy, associate director of the National Cancer Institute's surveillance research program, who led the study, said in a statement.
The results could help explain why reinfection seems to be relatively rare, and they could potentially guide future decisions about reopening work and school, as well as vaccine distribution choices.
According to the researchers, additional research is needed to understand how long that protection lasts, who may have less protection and how differences between patients, such as underlying conditions, might affect protection from reinfection.
The study was published Wednesday in JAMA Internal Medicine.
ABC News' Stephanie Ebbs contributed to this report.
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