Two research teams supported by Canada’s COVID-19 Immunity Task Force (CITF) are reporting initial findings about immunity to SARS-CoV-2, the virus that causes COVID-19, which we are announcing just as vaccine roll out has begun.

One of the teams, led by researchers at the University of Toronto, has had its initial work studying the immune response in COVID-19 patients published in the Journal of Immunology.

The findings that shed light on what is happening in the body may help to explain why patients with SARS-CoV-2 have more severe inflammation and lung tissue damage than patients suffering from regular seasonal influenza virus.

“We took blood cells from 13 people who had recovered from SARS-CoV-2 within the preceding 4-12 weeks,” explains researcher Tania Watts, professor in the Department of Immunology at the University of Toronto’s Temerty Faculty of Medicine and co-lead on the study. “We stimulated their blood cells in the lab with parts of the virus to see if their immune cells could recognize SARS-CoV-2 proteins and create a strong T cell response. We compared these responses to what we see with the common influenza virus, a virus to which most adults are immune and are exposed to often,” Watts continues. “All the SARS-CoV-2 recovered patients had immune memory responses to both SARS-CoV-2 and to the influenza virus, but with significant differences in how they responded.”

“The response in individuals whose blood cells were stimulated with SARS-CoV-2 showed increased inflammation and showed a response that implies less protection from infection than when people’s blood was stimulated with the influenza virus,” states study co-lead Mario Ostrowski, professor in the Departments of Medicine, Immunology, Laboratory Medicine and Pathobiology at the University of Toronto’s Temerty Faculty of Medicine.

“We need to find out whether the immune cells in the blood of someone who has recovered from COVID-19 will react similarly or differently to a vaccine for SARS-CoV-2. Will they have a more inflammatory and less protective response? With plans to vaccinate Canadians in full swing, it is important to continue to evaluate how people who previously had COVID-19 will respond to vaccines,” he continues.

The other research team, led by investigators at the Université de Montréal, will be looking into several questions over the coming months. “Can we predict which patients with SARS-CoV-2 infection will experience severe disease? Do survivors of COVID-19 develop long-term, protective immunity? Can antibody tests tell us which COVID-19 patients are at high risk of re-infection? And does re-exposure to the virus boost your immunity?” enumerates lead researcher Daniel Kaufmann, Professor at the Department of Medicine at the Université de Montréal.

Initial findings to one of these questions have been published in mBio, an open-access journal of the American Society for Microbiology. The team found that antibody levels in the blood of COVID-19 patients drop rapidly during the weeks after their immune systems have cleared the virus and symptoms have subsided.

“We were exploring the use of blood plasma from recovering patients as a possible treatment for patients with severe COVID-19 symptoms,” explains lead author Andrés Finzi, Canada Research Chair and associate professor at the Department of Microbiology, Infectiology et Immunology, Université de Montréal. “The blood of recovered patients contains antibodies that can act against the SARS-CoV-2 virus. However, our research shows that, if it is shown to have a clear benefit, convalescent plasma will need to be collected during a specific window of time after recovery. Since recovering patients can’t donate blood until at least 14 days after symptoms have subsided to give the body time to clear viral particles, the window will be tight,” Finzi says.

“Both of these research groups are part of the COVID-19 Immunity Task Force’s Immune Science Network,” says Dr. Catherine Hankins, Co-Chair of the CITF. “We are funding a number of studies on immunity and we’ve set-up networks like this one to encourage research teams to work together to align data, experiences, conclusions, methods – sharing as much as possible to make the research more effective and expedient,” she explains. “With the authorization of the first COVID-19 vaccine in Canada, researchers across the country are trying to speed up conclusions while ensuring rigorous methodology. At the Task Force, we continue to fund studies looking at immunity to get Canadians answers – and public health policy makers evidence to inform policies – as fast as possible.”

“These two research teams are among the many supported by the Government of Canada that are examining potential immune responses to COVID-19,” says Dr. Theresa Tam, Canada’s Chief Public Health Officer. “Having a better understanding of how the immune system responds in people who had COVID-19 and have recovered will allow us to plan and target our public health approaches, including immunization programs, more effectively.”

The funding for these two CITF-funded studies was announced in early September at the same time as 20 other studies were awarded funding. Both were peer reviewed through the Canadian Institutes of Health Research (CIHR)’s COVID-19 Rapid Research Competition. The University of Toronto research group is primarily funded by the CIHR. Original news release:

About the COVID-19 Immunity Task Force 

The Government of Canada launched the COVID-19 Immunity Task Force (CITF) in late April 2020 to track the spread of the virus in both the general population and priority populations in Canada. The Task Force also aims to shed light on immune responses to SARS-CoV-2 in a diversity of communities, age brackets, populations, and occupational groups across the nation. To generate this information, the Task Force is drawing on experts from universities and hospitals across Canada, working closely with provincial and territorial public health officials, and engaging communities/stakeholders from inception through to dissemination of findings. For more information visit:

Media Contacts

COVID-19 Immunity Task Force
Rebecca Burns, Cell: +1.438.871.8763
Caroline Phaneuf, Cell: +1.514.444.4532

University of Toronto Temerty Faculty of Medicine

Université de Montréal