TORONTO -- The World Health Organization (WHO) is opposing the use of “immunity passports” to allow people to leave self-isolation with a clean bill of health, noting it’s unclear how long immunity lasts after a patient recovers from COVID-19 — a view Canada's chief public health officer shares.

As countries around the world cautiously emerge from pandemic lockdowns, some have considered the use of so-called immunity passports as a way to identify citizens who have tested positive for COVID-19 antibodies.

Those who test positive would be allowed to return to work, shop, travel and circulate freely in public, while the non-immune remain in isolation.

But the WHO cautions that most of the studies regarding COVID-19 antibodies have been inconclusive and relying on antibodies as a way to reduce infections may have the opposite effect.

“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,’” read a scientific briefing posted to the WHO website Friday.

“People who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice. The use of such certificates may therefore increase the risks of continued transmission.”

Most studies show that people who have recovered from the novel coronavirus have antibodies to the virus. But the WHO said it’s unclear how long the protection from those antibodies lasts, making the efficacy of immunity passports unclear.

“So far, no studies have answered these important questions,” the WHO said in a statement.

Earlier in the day the WHO said there was “no evidence" that patients who have recovered from COVID-19 are protected from a second infection. However, the health organization clarified Saturday evening that most people who recover from COVID-19 have some level of protection, but scientists have yet to determine how long that protection lasts.


During his daily press briefing Saturday, Prime Minister Justin Trudeau said neither the federal nor provincial governments are basing plans to reduce lockdown restrictions on the possibility that people can develop an immunity to COVID-19.

“There is still an awful lot of science being done on the idea of immunity on protections, which is why we’ve invested significant amounts of money in a new Canada immunity taskforce that will be examining these issues,” he said.

“But it’s very clear that the science is not decided on whether or not having COVID once prevents you from getting it again… it is something that we need to get clearer answers to and until we have those clear answers, we have to err on the side of more caution.”

Chief Public Health Officer Dr. Theresa Tam said the immunity task force will play an important role in understanding how antibodies affect immunity, noting that there is still much to be learned about the novel coronavirus.

“We actually don’t understand the immunology of this virus very much,” Tam said Saturday during a press briefing.

“We don’t know when the peak of the antibody response might be reached, we definitely don’t know how long the antibody response might last for and what it means if someone gets infected.”

Germany, Italy and the U.K. have all floated the idea of using immunity passports in the next phase of their coronavirus response. Meanwhile, officials in New York state have already begun antibody testing, an effort Gov. Andrew Cuomo says could potentially help set policy on when to reopen parts of the state.

Despite questions surrounding immunity, Chilean government officials say they are moving with plans to offer the world’s first immunity passports to citizens. The country says 4,600 people have recovered from the virus and will now be eligible to receive a physical or digital card exempting them from quarantine rules.

While traditional COVID-19 testing strategies typically involve a nasal swab to detect a current infection, blood tests looking for antibodies are being developed rapidly all over the world, including in Canada.

Markham, Ont.-based biotechnology firm BTNX, for example, says it has developed a blood-based antibody test that looks similar to a pregnancy test and can deliver results in as little as 15 minutes.

The company previously told CTV News that Health Canada says the tests could not be sold in Canada until a “national strategy” on antibody testing is developed.

Health Canada did not respond to a request for comment from CTV News by the time of publication.

Tam noted Saturday that the reliability of these antibody tests has been varied because each test performs differently.

“Our national biology lab, having evaluated a range of tests, shows that a lot of them are not sensitive or specific enough,” she explained.

“Which means we could, in fact, get false positive where someone thinks they antibodies and they don’t.”

CTV News’ infectious disease specialist Dr. Abdu Sharkawy said the WHO is right to take a precautionary approach to the idea of immunity passports, highlighting previous evidence of the risk of re-infection.

“The concept that people could become re-infected after having recovered from COVID-19 is something we determined very early on in this pandemic,” he told CTV News Channel Saturday.

“We saw many case reports of this happening in Wuhan and Hubei province in China. The good thing is, that appears to be a relatively small number of people.”

Sharkawy notes that the medical community needs more time to confidently determine what level of antibodies need to be present in the blood stream to confer true protection before physical distancing measures can be relaxed.

“We can’t make recommendations that are going to be addressed to a whole society without knowing these tests are valid and without knowing what that true level of immune protection is needed,” he said.

“I think we will get there, but I think we need a little more patience and time.”

- With files from Avis Favaro