Doubts cast on Covid-19 reinfections

Some coronavirus patients in Korea who tested positive for Covid-19 after recovery ? sparking alarm about possible reinfections ? probably did so because the country’s sensitive testing procedure detected “dead” virus fragments within their bodies.

A clinical committee for new infectious diseases within the state-backed National Medical Center said Wednesday in a press briefing that there was a low chance that those people were actually reinfected with Covid-19 and said the country’s RT-PCR testing method seemed to have confused a dead virus fragment with an active one.

Fears of reinfection arose after the Korea Centers for Disease Control and Prevention reported cases of recovered patients testing positive for Covid-19 again. By Monday, there were at least 277 people who fell into that category.

Oh Myoung-don, a professor at Seoul National University’s College of Medicine, who leads the clinical committee, said the current RT-PCR testing method is unable to differentiate between an active virus and an inactive virus, which is probably why people who already recovered from the disease were testing positive again ? not because they were infected a second time.

RT-PCR is short for reverse transcription polymerase chain reaction, and the test works by tracking the Covid-19 virus’s genetic information in a sample taken from a person.

Based on his committee’s examinations, Oh said a person can test positive for Covid-19 when tested by the RT-PCR method as far as a month or two after full recovery even if they haven’t been reinfected, calling it an “intrinsic technical drawback” of RT-PCR testing.

The committee said there seemed to be “an extremely low chance” that a person who’s been infected by Covid-19 could contract the same virus shortly after his or her first infection. Research hints that a patient’s immunity against Covid-19 can last for at least a year, though further study is needed.

Yet the World Health Organization (WHO) warned Tuesday that there is currently “no evidence” that people who have recovered from Covid-19 and have antibodies are protected from a second infection, leaving open the possibility of reinfection.

“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 reinfection,” said the WHO.

“At this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an ‘immunity passport’ or ‘risk-free certificate,’” the WHO said.

The WHO guidance came amid reports that some countries were considering the issuance of so-called immunity cards for recovered Covid-19 patients, allowing them to individually travel or go to work based on the assumption that he or she can’t be infected a second time.

BY LEE SUNG-EUN [lee.sungeun@joongang.co.kr]