Canada's top doctor says there isn't enough evidence to back herd immunity as a way to reopen society, as Quebec's premier is considering the approach to restart his province's economy.
"The idea of ... generating natural immunity is actually not something that should be undertaken," Canada's Chief Public Health Officer Theresa Tam said Saturday, urging people to be "extremely cautious" about the concept.
Herd immunity is conferred when enough people in a given population have been infected with a virus, marking them immune to reinfection and slowing down the rate at which the virus spreads on its own.
The World Health Organization (WHO)
published a brief Friday stating that there is "currently no evidence" that people who have recovered from COVID-19 and have antibodies would be protected from a second infection, but clarified Saturday that most people infected would end up with "some level of protection."
Tam rejected the suggestion that in the absence of a vaccine, some members Canada's population could offer protection to society's most vulnerable.
"Even a young person might get severely sick or get into the ICU, so it's not a concept that should be supported," she said.
The prime minister said Saturday that those plans do not rely on using immunity as an interim form of protection.
"In the approach that we're taking very carefully around the provinces and across the country on looking at reopening, I don't believe that there are any plans that hinge on certain people or individuals being immune or having immunity to COVID-19," Trudeau said.
The federal government has
committed millions of dollars toward a new COVID-19 immunity task force focused on researching immunity testing and developing a vaccine — something Tam said is still in its early stages.
"Until we have those answers, we need to... err on the side of more caution," Trudeau said.
'Immunology' of the virus not known
Allowing people with protected immunity status back into society has captured international attention, with countries like Chile moving to issue "immunity passports" to those who have recovered from the virus.
The passes have been touted as a way to
gradually exempt people from restrictions put in place to limit the spread of COVID-19, permitting them to return to work, attend mass gatherings or even travel across borders.
But Tam warned that research on whether immunity is possible — and how long it might last — remains murky.
"It is a very novel virus," she said. "We don't understand the immunology of this virus very much."
