The novel coronavirus is, as the name suggests, a relatively new one, which means that scientists don’t have as much information about it as they do other viruses. Research is still ongoing, and there might not be solid information for some time to come. However, a new study may shed some light on one of the biggest questions out there — do people develop immunity after recovering from COVID-19?

As Bloomberg reports, a new study from the director of South Korea’s Centers for Disease Control and Prevention shows that it’s possible the virus may “reactivate” in individuals who are thought to have been cured of the illness.

One of the major questions facing scientists and experts hoping to predict and battle the coronavirus pandemic is whether or not people can test positive for the disease after initially recovering.

Over 50 people who tested positive for COVID-19 and were subsequently cured tested positive once again in South Korea. Dr. Jeong Eun-Kyeon said that patients are considered cured if they test negative two times during a 24-hour period. The patients were released from quarantine and tested positive shortly after, which seems to indicate a reactivation rather than reinfection, though more research is needed.

“While we are putting more weight on reactivation as the possible cause, we are conducting a comprehensive study on this,” Jeong said. “There have been many cases when a patient during treatment will test negative one day and positive another.”

South Korea was one of the first countries to be impacted on a large scale by the disease, but so far, it has only seen 200 deaths from COVID-19, as well as a peak of 1,189 new cases in one day. Part of that success is attributed to the country’s intense and widespread testing program. As a result, it was never forced to ask businesses to shut down or require people to shelter at home.

There have been other instances where patients have been suspected of getting sick again — or even dying from COVID-19 after being cured. In China, there have been a few instances of people leaving the hospital, only to come down with the disease once again.

It could be a matter of testing, but it could also indicate that individuals may not gain immunity to the illness.

Worldwide, there have been a total of nearly 95,000 deaths due to COVID-19, with the United States as the current epicenter. In the U.S., there have been 32,829 new cases in just one day, though some experts say that the spread of the disease may be nearing its peak.