The study shows that those infected are less likely to be infected.
Research shows that people who already infected with covid-19 have a low risk of re-infection, at least about three months later. The study is funded by the US government.
The study was published in the journal JAMA Internal Medicine and was developed by the National Cancer Institute (NCI) in collaboration with commercial testing laboratories and two health data collection companies. Unknown data from more than 3 million Americans who performed an antibody test to SARS-CoV-2 were analyzed. Based on the tests, people were divided into those with antibodies and those without them. The researchers then looked at how many people in both groups later underwent a PCR test for COVID-19 to diagnose active infection.
About 10% of the people in each group passed the PCR test. More people with antibodies tested positive for the virus in the first 30 days after antibody testing than those without antibodies. But this is not surprising, as the perceptible traces of the virus can remain in the body for months.
After three months or more only 0.3% of people with a previous positive antibody test were positive for coronavirus again. “People who have survived COVID-19 need to be convinced that the presence of positive antibodies is associated with some protection against re-infection,” said study author Douglas Lowy, senior deputy director of NCI.
Nevertheless the study does not indicate how much protection the past infection will provide against re-infection or its duration. There is currently no research to show that currently expanded versions can completely circumvent natural immunity.