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The Covid-19 'immunity passport', how reliable is it?

Chile is set to be the first country in the world to issue an immunity certiifcate, or 'Covid Card' for patients recovered from coronavirus. But experts question the reliability of antibody tests and warn they may not be a guarantee of protection against re-infection. (Para leer en español)
27 Abr 2020 – 06:48 PM EDT
A police officer wearing a face mask controls access of a driver to the quarantine area during the first day of the lock down in seven communes of the capital on March 27, 2020 in Santiago, Chile. Crédito: Marcelo Hernandez/Getty Images

Chile plans to become the world’s first country to issue immunity cards for recovered covid-19 patients despite a World Health Organization warning that there was no evidence they are protected from a second coronavirus infection.

Paula Daza, sub-secretary of Chile’s Health Ministry, told reporters on Sunday that the cards will soon be delivered to patients. She insisted that while uncertainties still exist about the protection anti-bodies can give to someone who has had covid-19, evidence suggested there was a reduced risk after a first bout of coronavirus.

“One of the things we know is that a person who has ... lived through the disease is less likely to become ill again,” Daza said.

Chilean officials say the cards, known as “release certificates” that it plans to issue are not intended to certify or prove medical immunity with 100% certainty.

Freed from quarantine

But it was unclear how the certificates will be used. Other Chilean officials have said those issued the cards would “freed from all types of quarantine or restriction” since they pose no risk.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said recently that it’s “possible” that Americans may be given similar forms of identification.

“This is something that’s being discussed,” Fauci told CNN. “I think it might actually have some merit, under certain circumstances.”

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WHO warning

The WHO, which is an agency of the United Nations, on Saturday warned governments against issuing “immunity passports” to people who have been infected as their accuracy could not be guaranteed.

The WHO said issuing the certificates could inspire false confidence and increase the risk of spreading the virus. People who have recovered may ignore advice about taking precautions against the virus, the WHO said.

“There is currently no evidence that people who have recovered from covid-19 and have antibodies are protected from a second infection,” it said.

Public officials are hopeful that antibody tests which show who has been infected could serve as a useful tool to guide them on how to reopen communities. Immunity card could in theory be used to identify people who can safely go back to work without infecting other people.

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New York and Miami

A survey of New Yorkers last week found that one in five city residents carried antibodies to the new coronavirus. Another study in South Florida found that about six percent of Miami-Dade’s population, or roughly 165,000 residents, have antibodies indicating a past infection by the novel coronavirus, much larger than the state health department’s tally of about 10,600 cases, according to University of Miami researchers.

That conclusion was based on a random selection over the last two weeks of about 1,400 residents who volunteered pinpricks of their blood to be screened for signs of a past covid-19 infection, whether they had tested positive for the virus in the past or not.

It found that about half of the people who tested positive for antibodies reported no symptoms in the 14-17 days before being tested.

But antibody tests are often inaccurate, recent research suggests, and it is not clear whether a positive result actually signals immunity to the coronavirus, according to The New York Times. Some produced potentially dangerous false-positive results, that could lead to people mistakenly believing they are immune to the virus and then putting themselves – and others - in danger by abandoning social distancing measures.

There have also been reports, notably from South Korea, of cases of people who had covid-19 and got infected again after their quarantine ended.

Most studies carried out so far showed that people who had recovered from infection had antibodies in their blood, though they may have varying levels which could affect their potential immunity.

The New York Times reported that more than 50 scientists have been working to verify if 14 of the different coronavirus antibody tests now on the market actually deliver accurate results.

The new research, posted online Friday, found that of the 14 tests, only three delivered consistently reliable results. Even then the best three tests detected antibodies in infected people only 90 percent of the time. Four of the tests produced false-positive rates ranging from 11 percent to 16 percent; lothers were around five percent.

The study was part funded by the Chan Zuckerberg Biohub, a medical science research center funded by Facebook CEO, Mark Zuckerberg, and his wife Priscilla Chan.

Rush to get tests

Already Americans are scrambling to take antibody tests to see if they might escape lockdowns.

"Somehow knowing for certain that I carry the antibodies will give not only a sense of physical security; it will be liberating," said one 63-year-old businessman in South Florida who preferred not to be named. He said he was awaiting a test appointment on Wednesday.

"I’ll know I’m wearing a mask and keeping distance due to solidarity, and not due to need. I’ll be able to get back to my regular business travel ... and giving a friend a handshake will really mean something," he added, though he said he was aware the testing was not foolproof.

The $65 test involved a straightforward pin prick to the finger, with an answer available in less than 15 minutes. The tests are available at certain pharmacies after filling out application forms, but there is a long backlog with waiting times currently running up to a month.

Testing ramping up worldwide

Many countries including the United States, Chile and several European countries are beginning to test samples of their populations for antibodies. In the UK, 25,000 people will be tested every month for the next year - both for antibodies, and to check if they currently have the virus, the BBC reported.

But some experts strongly oppose the idea of immunity passports, warning they might create moral and criminal issues, such as forgeries and people deliberately infecting themselves with the virus, as happened during the 1918 Spanish flu.

In Chile, anyone can apply for the cards, which are due to be issued starting Monday. To qualify, Chileans have to take a test that shows they have antibodies for covid-19. Those who have had the disease must be free of symptoms for at least 14 days.

Chile has confirmed 13,331 cases of coronavirus, as well as 189 deaths, and has seen the curve of infections flatten in recent weeks.

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