People who recover from COVID-19, test positive again not contagious, Korean study suggests

A new study out of South Korea suggests that people who test positive for COVID-19 a second time may no longer be contagious.

For the study, published Tuesday by South Korea's Centers for Disease Control and Prevention, researchers looked at 285 COVID-19 patients who tested positive, then negative, and then positive again, said Dr. Jen Ashton, ABC News chief medical correspondent.

These patients were re-positive anywhere from eight to 82 days after their initial onset of symptoms.

Ashton said researchers used coronavirus samples collected in nasal swabs and found that none of them grew in culture, suggesting that viruses could be dead.

They also checked the blood from a small subset of patients and found that most had neutralizing antibodies that protect them from getting sick again.

"However, some of these people did have symptoms. Right now, it's not clear whether they continue to shed virus or whether this is a reactivation, just like we see, for example, in chickenpox and shingles," Ashton said.

Because of this study, KCDC said it is lifting the requirements that people recovering from a COVID-19 infection need to have a negative test result to return to work or school.

Ashton said this finding could be helpful to health authorities in the United States.

"It may be that this information can be used to help determine whether people who have been positive can go back to work or school. Right now, we're not using testing to help guide that, but we'll see if that evolves in the future. That's all to be determined," she said.