"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's comments come as Quebec Premier François Legault expressed interest in herd immunity this week as a means to reopen businesses and allow children to return to school.
"The idea is to gradually — and that's the important word — to gradually let people go out, let children go out," he said Thursday, adding that those under 60 years of age might be candidates for developing immunity.
Tam rejected the suggestion that in the absence of a vaccine, some members of 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.
In response to Tam's remarks, Premier Legault's office said the province plans to forge ahead with easing lockdown restrictions, but only with the approval of Quebec's public health department.