Antibodies Protect Against COVID-19 Reinfection

A cell from a patient (purple) infected with SARS-CoV-2 (blue). NIAID

After having COVID-19, most people’s bodies develop antibodies to help fight it off. These are special molecules made by the body’s disease defense system, the immune system. A study found that people with these antibodies were less likely to get COVID-19 again.

Researchers looked at more than 3 million people who had an antibody test for SARS-CoV-2. SARS-CoV-2 is the virus that causes COVID-19.

They found that about 11% of people had SARS-CoV-2 antibodies. More than 88% had a negative test. And less than 1% of tests were inconclusive.

The scientists looked at who came down with COVID-19 after the test. They analyzed up to 30 days, 31–60 days, 61–90 days, and more than 90 days after.

About 3% to 4% of people with negative antibody tests got COVID-19 in each time period. But those who had antibodies were less likely to have COVID-19 as time went on. Only 0.3% of the people with antibodies had a positive COVID-19 test more than 90 days after. Those without antibodies were 10 times more likely to get the disease.

The findings suggest that people who have a positive result from an antibody test may be at lower risk for future infection with SARS-CoV-2.

NIH’s Dr. Lynn Penberthy, who led the research team, explains that more questions still need to be answered. “We are nevertheless encouraged by this early finding,” she says.