Survivors of COVID-19, who tested positive to coronavirus after recovery, are not capable of transmitting it the second time, a new study finds.
Researchers from the Korea Center for Disease Control and Prevention (KCDC), in a study, looked at 285 survivors who tested positive after previous tests said they were negative.
The study reported late Monday revealed that the virus samples collected from the patients who tested positive a second time could not be grown in lab cultures.
“This suggests the patients were not re-infected but rather that they were shedding dead virus particles,” the study said.
After health authorities in South Korea raised alarms last month upon dozens of recovered patients testing positive for the virus again, the results of the study were accepted.
“None of the 790 people that the patients came into contact with were found to be infected with COVID-19, the disease caused by the virus,” the study said.
More than 400 people have reconfirmed cases of the virus, according to the KCDC.
“Because of the study’s results, South Korean health officials will no longer consider people infectious after they recover from COVID-19,” the KCDC said.
The agency said after recovering or completing an isolation period, residents will not have to test negative for the virus before returning to school or work.
“Under the new protocols, no additional tests are required for cases that have been discharged from isolation,” the KCDC wrote in a report, according to Bloomberg.
KCDC said cases in which someone has tested positive again will not be referred to as PCR re-detected after discharge from isolation.
However, it remains unclear how many antibodies one needs to prevent being re-infected and how long they remain in the body.
A recent study in Singapore showed that patients who have recovered from severe acute respiratory syndrome, or SARS, are found to have “significant levels of neutralizing antibodies” nine to 17 years after initial infection, according to researchers including Danielle Anderson of Duke-NUS Medical School.
Other scientists have found higher levels of IgM, an antibody that appears in response to exposure to an antigen, in children, according to an article published on medRxiv.
This suggests that the younger population have the potential to produce a more potent defence against COVID-19. The study has not been certified by peer review.
The World Health Organization (WHO), however, advised against this and said the accuracy of such documents could not be guaranteed.
‘Some governments have suggested that the detection of antibodies to the SARS-CoV-2, the virus that causes COVID-19, could serve as the basis for an ‘immunity passport’ or ‘risk-free certificate’ that would enable individuals to travel or to return to work assuming that they are protected against re-infection,’ the WHO said in a statement.