More than two years into the COVID-19 pandemic and months after the onset of the Omicron variant, roughly a third of the Canadian population has been infected with the virus, according to an expert and mounting research.
Dr. Catherine Hankins, co-chair of the COVID-19 Immunity Task Force, told Global News that the Omicron variant that hit Canada starting in November 2021 had evaded immunity, leading to reinfections and breakthrough cases.
“I would think after two years, it’s very likely now that a third of the population has had a COVID infection,” Hankins said.
“Omicron had an ability to evade the antibodies that we had built up from either a previous infection or vaccination.”
An April 10 report based on seroprevalence analysis—which measures the level of a pathogen in a population through blood samples—shows that the highly-contagious Omicron variant had doubled Canadian’s natural infection rate.
The report tracked COVID-19 seroprevalence to distinguish natural and vaccine-induced humoral immunity since the beginning of the pandemic. In this latest update that analyzed data in the month of February, the infection-acquired seropositivity averaged 23.7 percent nationally—a two-fold jump from January’s rate.
“While humoral immunity was largely driven by vaccination, the fraction of the population naturally exposed has increased sharply since December consistent with the arrival of the Omicron variant,” says the report, jointly conducted by the COVID-19 Immunity Task Force and Canadian Blood Services.
The data for the study is based on blood samples collected by Canadian Blood Services. The organization has blood collection sites in all large cities and many smaller urban centres in all provinces except Quebec; blood donations are also not collected in the northern territories. Blood donors are reasonably representative of healthy Canadians between the ages of 17 and about 60.
Seroprevalence rates increased in February compared to January in all provinces, with Alberta, Manitoba, and British Columbia having the highest infection rates, the report says.
Young Canadians between the age of 17 and 24 age had the highest natural infection levels at 36.3 percent compared to other age groups, which remains consistent with previous surveys.
Similar studies to track the SARS-CoV-2 antibodies in blood samples since the beginning of the pandemic have also been carried out by the British Columbia Centre for Disease Control (BCCDC), in partnership with LifeLabs.
Their analysis also reveals the significant impacts of the Omicron variant on the Canadian population.
Dr. Danuta Skowronski, lead researcher and epidemiologist at BCCDC, told Global News that in their latest seroprevalence survey, over 40 percent of the B.C. population had infection-induced antibodies as of March 2022. In contrast, up until fall 2021 before the onset of the Omicron wave, only 10 percent of the province’s population had been infected.
Children were the most affected group, with about two-thirds under the age of 10 having caught the virus, she said.
“We’ve gone from a population with near-total susceptibility to the virus, whereas now more than 90 percent of us have had some sort of priming, either through vaccination or infection,” she said.