THE WORLD HEALTH Organisation (WHO) has warned against the idea of “immunity passports” amid the coronavirus pandemic.

It said there is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected against a second infection.

The concept of “immunity passports” or “risk-free certificates” has been floated as a way of allowing people protected against reinfection to return to work.

But the Geneva-based UN health agency said in a scientific brief published on Saturday that more research is needed.

It said that “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’.”

It argued that people who assume they are immune to reinfection may ignore public health advice, and that such certificates could raise the risks of continued virus transmission.

The WHO added that tests for antibodies of the new coronavirus also “need further validation to determine their accuracy and reliability”.

A recent study from China that has not gone through peer review reported on rhesus monkeys that recovered from Sars-Cov-2 and did not get reinfected when exposed once again to the virus.

“But that doesn’t really reveal anything,” said Pasteur Institute researcher Frederic Tangy, noting that the experiment unfolded over only a month.

Indeed,several cases from South Korea — one of the first countries hit by the new coronavirus — found that patients who recovered from COVID-19 later tested positive for the virus.

But there are several ways to explain that outcome, scientists cautioned.

While it is not impossible that these individuals became infected a second time, there is little evidence this is what happened.

More likely is that the virus never completely disappeared in the first place and remains — dormant and asymptomatic — as a “chronic infection”, like herpes, according to Francois Balloux ,director of the Genetics Institute at University College London

As tests for live virus and antibodies have not yet been perfected, it is also possible that these patients at some point tested “false negative” when in fact they had not rid themselves of the pathogen.