Analysis of blood test data


MONTREAL, July 06. 28, 2022 (GLOBE NEWSWIRE) — An analysis of data from 21 studies, funded by the Government of Canada through its Task Force on COVID-19 Immunity (GTCI), that relied on tests blood, provides a clearer picture of the massive scale of the Omicron wave in Canada. Before the arrival of the Omicron variant, about 7% of Canadians had acquired antibodies against SARS-CoV-2, the virus that causes COVID-19. Between December 2021 and May 2022, the proportion of Canadians with antibodies against SARS-CoV-2 infection increased by 45% (see Figure 1 below). A fuller account of the analysis can be found online here.

“Omicron has been a tsunami,” says CITF Executive Director Dr. Tim Evans. “Across the country, our analysis of the data suggests that 17 million Canadians had an infection with Omicron during the period from December to May, for an average of more than 100,000 infections per day. New sublines of the Omicron lineage have continued to spread since then, and the percentage of Canadians who have had SARS-CoV-2 infection is now likely well over 50%. »

All affected provinces

The number of people with signs of a previous infection in their blood (seroprevalence acquired by infection) increased sharply during the Omicron wave in each province (Figure 2). At the end of May, the proportion of people with signs of previous infection was 50-60% in the western and central provinces. Although Atlantic Canada maintained the lowest seropositivity due to infection, it experienced the largest relative increase in seroprevalence, reaching over 35%.

Omicron has affected all ages – but the youngest and least vaccinated populations the most!

Analysis of blood donations made to Canadian Blood Services (which provides the CITF with an update every two weeks) showed that the highest levels of seropositivity due to infection were in young adults, with around 65% having antibodies as of the last week of May. Seropositivity rates due to infection decreased with age: 25-39 (57%), 40-59 (51%) and 60+ (31%) (Figure 3).

“Thanks to the sheer number of infections, the Omicron variant has taken a heavy toll in terms of services and disrupted lives, as well as hospitalizations and deaths. This has clearly not spared healthy young Canadians,” CITF Co-Chair Dr. Catherine Hankins said, “Additionally, we’re still learning who gets a post-COVID-19 condition or long COVID, why, and the repercussions. This summer may be free of public health restrictions, but Omicron continues to spread, so masking and distancing is smart in at-risk environments. To minimize further disruption to our lives, Canada must closely monitor the evolving situation. We all need to respond in time timely because this virus does not have a seasonal pattern, like other respiratory viruses we expect when everyone returns to work or school in the fall.

“Millions of Canadians now have hybrid immunity to a combination of COVID-19 vaccines and infection. Unfortunately, new evidence suggests that most of these individuals remain at risk of reinfection with Omicron lineage viruses,” says CITF Co-Chair Dr. David Naylor. He adds: “New vaccines can improve coverage against infection. However, we still have millions of adults who have not received a third injection and should get one to strengthen their protection against serious diseases. More generally, all Canadians should stay tuned for the latest public health guidance on COVID-19 vaccines and ensure their coverage is up to date for the fall season.

About the COVID-19 Immunity Task Force

The Government of Canada has established the COVID-19 Immunity Task Force (CITF) end of April 2020 to catalyze, support and harmonize SARS-CoV-2 immunity research for federal, provincial and territorial policy makers in their efforts to protect Canadians and minimize the impact of COVID-19. The task force and its secretariat work closely with a range of partners, including governments, public health agencies, institutions, health organizations, research teams and other task forces, engaging communities and stakeholders. To date, the CITF has supported more than 100 studies across Canada that generate information on the levels, trends, nature, and duration of immunity from SARS-CoV-2 infection and vaccination against COVID-19. CFTF is overseen by a volunteer executive committee that includes leading scientists and policy makers from across Canada.

Media contact

Rebecca burns
[email protected]
Cell: +1.438.871.8763

Figure 1. Anti-nucleocapsid seroprevalence (seropositivity acquired by infection) for all Canadian provinces for all age groups, combined

Figure 2. Estimates of anti-nucleocapsid seroprevalence (seropositivity acquired by infection) by province

COVID-19 Immunity Task Force

Figure 3. Estimates of anti-nucleocapsid seroprevalence (seropositivity acquired by infection) by median age

COVID-19 Immunity Task Force

The views expressed here do not necessarily represent the views of the Public Health Agency of Canada.

Graphics accompanying this announcement are available at

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