COVID-19: Does Past Infection Provide Future Protection?

With nearly 29 million cases of COVID-19 in the United States so far, many people are wondering whether past infection will protect against future infection.

A new study has an answer: People who appear to have had COVID-19 in the past seem to be well-protected against infection with COVID-19 for at least a few months.

This study from the National Institutes of Health (NIH) helps explain why COVID-19 reinfection is somewhat rare, according to the study authors.

The researchers behind this study looked at COVID-19 antibody test data from two health care data companies and five commercial labs.

“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,” said lead study author Dr. Lynne Penberthy, associate director of the National Cancer Institute's Surveillance Research Program, in a press release. “Additional research is needed to understand how long this protection lasts, who may have limited protection, and how patient characteristics, such as comorbid conditions, may impact protection. We are nevertheless encouraged by this early finding.”

In total, this study looked at antibody test results for more than 3 million people. According to the NIH, this represented more than half of the antibody tests given between January and August of last year. Almost 12 percent of the tests were positive for COVID-19 antibodies. A few were inconclusive, and the rest were negative.

Over the course of the study, those who did not have COVID-19 antibodies later tested positive for the virus at a rate of 3 to 4 percent. For those who did have antibodies, the future positivity rate was 0.3 percent.

This suggests that having COVID-19 antibodies was tied to a much lower chance of getting COVID-19 later on, the study authors noted.

These researchers noted that their study did not look at long-term protection against COVID-19. They called for further research to address this topic.

This study was published in the journal JAMA Internal Medicine.

Information on funding sources and potential conflicts of interest was not available at the time of publication.