It remains unclear whether people who have been infected with the coronavirus are at risk of becoming infected again, the World Health Organization said Wednesday.
"The jury is still very much out on that," Dr. Mike Ryan, executive director of the WHO's emergencies program, said during a press conference at the agency's Geneva headquarters.
Scientists are still learning about key aspects of the virus, including how immune systems respond once a person is exposed.
Researchers from the Korean Centers for Disease Control and Prevention published a report last week that studied patients who tested positive for Covid-19 again after recovering and getting discharged from isolation.
They found that re-positive cases carried the antibodies that would protect them from falling ill again and few healthy people who were exposed to the reinfected patients contracted Covid-19 themselves. That led researchers to conclude the reinfected people were "re-detected" and not a threat if released from isolation. That should be good news for those who have recovered and wish to head back to work, but it's not definitive proof yet.
Ryan said Wednesday that there is some evidence that former Covid-19 patients with virus-killing T cells may be able to mount a more "rapid response" against the virus. But there is no empirical evidence that previous coronavirus infections protect patients from re-infection, he said.
He said some studies suggest patients produce a broad-based immune response to the virus, which he said may be helpful as scientists work to develop a vaccine for Covid-19.
Last month, WHO said scientists still don't know whether coronavirus antibodies give a person immunity or reduce the risk of reinfection, even as some nations consider issuing passports or certificates that indicate whether someone has had the virus.