But while herd immunity may be elusive, stopping transmission with vaccines can restore a similar semblance of normalcy, she said. Catherine Hankins, the co-chair of Canada’s COVID-19 Immunity Task Force, says factors like the coronavirus variants-of-concerns may mean Canada doesn't achieve herd immunity any time soon — or at all. (Submitted by Catherine Hankins ) Herd immunity occurs when enough of a population is immune to a virus — either naturally from infection or through vaccination — so the virus can't find hosts and eventually dies off. The threshold for herd immunity is different depending on the virus. For COVID-19, people initially thought we'd need about 60-70 per cent of the population to be immune in order to achieve it, said Hankins