April 23, 2020 – January 25, 2021

In any viral pandemic, effective responses are heavily influenced by the virus itself: its virulence, infectivity and patterns of spread, seasonality, ratios of symptomatic to asymptomatic cases, induced immune responses, and mutations over time.
Various public health measures are deployed to prevent and respond to epidemic waves, until eradication is achieved, or a very high level of background immunity is reached.
This timeline encapsulates the evolving agenda of the COVID-19 Immunity Task Force [CITF].

  • As Wave 1 receded, the CITF worked with a number of partners, including Canadian Blood Services (CBS) and Héma-Québec, to uncover previously undetected COVID-19 infections by measuring antibodies to the novel coronavirus (SARS-CoV-2) in blood samples. These ‘seroprevalence’ tests showed that few Canadians had infection-acquired immunity. This low background immunity was highlighted by national and provincial public health officials who warned repeatedly that it signalled substantial pan-Canadian vulnerability to a second wave of COVID-19.
  • As Wave 2 built, the CITF built new partnerships to deepen its understanding of the prevalence of COVID-19 and immune responses to it. The CITF adjusted strategy based on earlier findings. It supported ongoing ‘serosurveys’ (analyses of large numbers of samples for antibodies to SARS-CoV-2) but added a range of focused seroprevalence studies across age brackets, targeting occupations-at-risk, and ‘hot spots’ such as long-term care settings and racialized neighbourhoods. Testing technologies were also developed and validated to enable analysis of both infection-acquired and vaccine-induced immunity from diverse sources, including self-administered finger-prick kits.
  • With Wave 2 continuing and vaccines arriving, in November leaders of all relevant CITF-sponsored studies were asked to develop data collection plans to help inform the safe and effective roll-out of vaccines. Since then, under the auspice of the Public Health Agency of Canada [PHAC], the CITF has joined a coalition led by vaccinology experts from across Canada. Work by this new Vaccine Surveillance Reference Group [VSRG] will permit national tracking of the path to herd immunity through infection-acquired and vaccine-induced immunity.  

Wave 1 – and Aftermath

On January 23, 2020, Patient Zero was admitted with COVID-19 pneumonia at Toronto’s Sunnybrook Health Sciences Centre. Daily case counts remained low at first, but by March 11th there was formal national recognition of the threat. Containment and other control measures were ramped up, but case growth accelerated. Wave 1 of COVID-19 in Canada peaked in early May. It then receded steadily through to early summer due to seasonal factors, and a range of public health interventions, not least of which were mitigation tactics that extended to full lockdowns in multiple provinces.

  • The CITF was launched near the peak of the first wave. About 50 days later, CITF-supported affiliates set up SeroTracker — the first and only global monitoring site for seroprevalence studies.
  • For a first scan of background immunity, the CITF supported analyses of available blood samples carried out by Canadian Blood Services and Héma-Québec. Use of these ‘convenience samples’ made it possible to catch the May-June tail of Wave 1. Initial results were reported out in July and August, showing very low prevalence – highest at 2.2% in Quebec, which had been hardest hit in Wave 1, and averaging only 0.7% for the nine other provinces. 
  • The results were shared widely and reported nationally by media outlets. The implication was clear. Notwithstanding conspicuous failures to protect seniors and others in congregate care or assisted residential settings, Canadians everywhere had helped contain wide community spread. But low background immunity also meant little resistance to new waves of COVID-19 in the months ahead.   
  • The two blood agencies continued accruing samples. Further results were obtained in late August and September, confirming – as expected – little change in seroprevalence as the daily caseloads remained low across Canada. 
  • These numbers corresponded with results from assessments of seroprevalence undertaken by provincial public health laboratories in Alberta, BC, and Ontario on blood samples collected for disease surveillance. (The CITF provided assays for these assessments in Alberta and Ontario, as part of a standing offer of support to any of the 13 provinces and territories that needed funding or technical advice.) Even after allowing for downward biases inherent in these sampling frames, Canadians remained highly vulnerable to a second wave when the colder weather arrived.

The implications of these results were strongly reinforced by federal and provincial public health officials.

Wave 2 – Continuing and continuing…

In mid-August, Canadian COVID-19 swab-confirmed caseload numbers began creeping upwards. By mid-October, 7-day averages of new cases had eclipsed the peaks seen in Wave 1 and continued to climb through November and December. Regions that had contained spread – the northern territories and Atlantic Canada with its remarkable multi-province ‘bubble’ – were hit by outbreaks, as were numerous remote Indigenous communities. All other provinces saw substantial community spread. National 7-day averages of new cases peaked about five times higher than in Wave 1. They appear to be trending back down now in January 2021 with widespread lockdowns.

  • Both the demography of cases and the extremely low seroprevalence rates in the aftermath of Wave 1 sparked discussion in the CITF about timing, targeting, and scale of further studies to track background immunity, as well as the lack of detail about study subjects when bloods were derived from ‘convenience samples’.  Targeted studies were funded, e.g. adding seroprevalence assessments to established Canadian cohort studies that had accumulated relevant information over many years on consenting seniors living in the community (e.g. CLSA) as well as younger individuals (e.g. CanPath) over many years. 
  • A partnership with the Canadian Institutes of Health Research [CIHR] allowed the CITF to piggy-back on an existing research funding competition and fund or co-fund multiple high-quality studies. Twenty-two projects came out of this collaboration, including seroprevalence studies focused again on targeted populations (e.g. children and healthcare workers), immune science studies, and testing science studies.
  • The CITF also created networks supporting and linking several of these studies, promoting sharing of ideas, methodology, and data to render the studies more effective and efficient.
  • Support for all funded large-scale serosurveys followed a phased approach whereby an assessment of initial results informed decisions to optimize the value of any further funds invested.
  • At the same time, faced with no Canadian government-approved at-home antibody tests, the CITF intensified work with the National Microbiology Laboratory to get full validation of a dried blood spot [DBS] test for SARS-CoV-2 antibodies that could be done on specimens self-obtained at home. Sending these DBS kits to people’s homes, rather than having them go for blood draws at a test centre, would allow many more Canadians to participate in immunity studies.
  • The validation of dried blood spots was completed in September. It has enabled broadly-based studies to proceed with home testing. Among them is the national study by Statistics Canada that is now in the field that will cover all age brackets and locations to reflect COVID-19 seroprevalence right across Canada. Like others of our studies, the StatCan project includes vaccine questions, and the testing technology can distinguish infection-acquired immunity from vaccine-induced immunity. It should provide invaluable insights as vaccines roll out in the months ahead. 
  • In Wave 2 as in Wave 1, the virus continued to take its largest toll on seniors and others in long-term care or assisted residential settings. It also struck hard at neighborhoods with racialized populations, and clusters occurred in multiple congregate workplaces. Recognizing these unequal risks, the CITF gathered ‘hot spot’ proposals from across Canada and supported focused studies to assess seroprevalence and how immunity works in these vulnerable populations. For example, over 30,000 long term care residents from Vancouver to Halifax are now enrolled in a network of long-term care studies.   


Wave 2 continuing — Vaccines and Variants arrive

In December 2020, as Wave 2 moved rapidly to a crest, the first SARS-CoV-2 vaccines arrived in Canada, along with news of ‘variants of concern’ in other jurisdictions. Canada aims to immunize three million people by the end of March 2021. Q1 should cover most front-line healthcare workers, seniors, and others in congregate care/residential settings, many remote Indigenous and northern communities, and a proportion of seniors at home. The goal for Q2: Immunize at least 20 million more Canadians in what is now a race to stop a possible Wave 3 fuelled by more infectious viral variants.

  • In November 2020, with vaccines looming, the CITF formally adopted a Phase 2 strategy. This strategy draws on the portfolio of 55 CITF studies and identifies areas for further work to support and monitor safe and effective rollout of vaccines. The work plan includes scaling up made-in-Canada testing capacity that can distinguish between vaccine-induced and infection-acquired immunity.   
  • Canadian Blood Services survey results from November show notable regional hotspots that have emerged, particularly in Manitoba and Saskatchewan where provincial seroprevalence averages are now 8.56% and 4.2% respectively. Disparities by ethnicity are clear, but overall seroprevalence across Canada remains low at 1.51%, highlighting the urgent need for vaccines.
  • In December, under the auspices of the President of PHAC, the CITF joined discussions about the vaccine roll-out with the National Advisory Committee on Immunization [NACI], the Canadian Immunization Research Network [CIRN], the Vaccine Task Force, the Chief Scientist, and CIHR.
  • The CITF’s Secretariat and budget will now be marshalled to support a new Vaccine Surveillance Reference Group, co-led by the Chair of NACI and the Principal Investigator of CIRN (both CITF members). The new group will work closely with a range of partners, including provinces and territories, to monitor the safe and effective roll-out of SARS-CoV-2 vaccines across Canada in the months ahead.

About the Canadian COVID-19 Immunity Task Force: In late April 2020, the Government of Canada established the COVID-19 Immunity Task Force with a two-year mandate. Working virtually, the Task Force Leadership Group is a representative set of volunteer experts from across the country who are focused on understanding the nature of immunity arising from the novel coronavirus that causes COVID-19, and the prevalence of that infection in the general population, specific communities, and priority populations. The Task Force and its Secretariat accordingly work closely with a range of partners, including governments, public health agencies, institutions, health organizations, research teams, other task forces, communities, and stakeholders. Most recently, the Task Force has been asked to take a major role in supporting vaccine surveillance for effectiveness and safety. Our overriding objective is to generate data and ideas that inform interventions aimed at slowing and ultimately stopping the spread of SARS-CoV-2 in Canada. For more information visit: www.covid19immunitytaskforce.ca