The COVID-19 Immunity Task Force (CITF) was created in late April 2020 with the goal of catalyzing, supporting, funding and harmonizing research into COVID-19 immunity to inform Canadian policymakers, allowing them to make evidence-based decisions. The Task Force completed its mandate on March 31, 2024.

Throughout its nearly four-year run, the CITF supported numerous studies in order to:

  • Determine the extent of SARS-CoV-2 infection and vaccination in the general Canadian population as well as in specific communities and priority populations;
  • Understand the nature of immunity arising from SARS-CoV-2 infection and vaccination;
  • Develop improved antibody testing methods;
  • Monitor the effectiveness and safety of vaccines as they were rolled out across Canada and in specific sub-groups of the population such as children;
  • Determine the need for, and optimal timing of, booster shots;
  • Develop models of population immunity to guide our national public health efforts as the pandemic continued to evolve; and
  • Monitor immunity arising from multiple SARS-CoV-2 VOCs, as well as hybrid immunity.

The Task Force and its Secretariat worked closely with a range of partners, including governments, public health agencies, institutions, health organizations, research partners, other task forces, and also engaged communities and stakeholders.

Data from eligible CITF funded studies were centralized and are now available for further study through the CITF Databank.


Pivoting with the pandemic

Just as the pandemic was constantly evolving, so too did the work of the CITF. Starting in April 2020, the Task Force moved through three strategic phases with the aim of mobilizing knowledge required by decision-makers to mitigate the effects of the COVID-19 pandemic across Canada. A fourth phase was a wrap-up phase.

Phase 1

Phase 1, from May 2020 to November 2020, was focused on the development and mobilization of studies looking at:

  • The levels and trends in SARS-CoV-2 infection through seroprevalence The proportion of people in a population who test positive for a specific disease based on antibody or serology tests. surveys across age-groups, risk groups, and geographies in Canada. This involved assessing SARS-CoV-2 antibodies amongst blood donors, participants in existing research platforms and in transmission hot spots;
  • The degree and duration of immune protection arising from infection, along with the risk of reinfection, by following people infected with SARS-CoV-2 over a long period of time;
  • How best to measure immunity linked to SARS-CoV-2 for diverse purposes. This included evaluating diverse assays (tests) and modes of blood collection, such as a traditional blood sampling with a needle vs. a fingerprick (or dried blood spots); and
  • Compiling seroprevalence findings in Canada and across the globe into easy-to-read dashboards through support for the creation of SeroTracker.

Phase 2

Phase 2, December 2020 to June 2021, corresponded with the approval and roll out of vaccines for COVID-19 with studies focusing on vaccine safety, effectiveness, and immunogenicityThe ability of a substance to provoke an immune response or the degree to which it provokes a response.. CITF investments aimed to:

  • Increase the scope and scale of existing Canadian networks to monitor vaccine safety and effectiveness alongside the most extensive vaccine rollout in Canadian history;
  • Explore SARS-CoV-2 vaccine effectiveness and safety in populations that were understudied in clinical trials, such as racialized and Indigenous communities, older adults, people at high risk due to existing health conditions, people with social or occupational vulnerabilities, and individuals who were pregnant or breastfeeding, among others;
  • Determine the various aspects of COVID-19 vaccines: how long their protective effects last, whether mixing and matching vaccines could provide equal protection to two doses of the same vaccine, and whether prolonged intervals between doses is as – or more – effective than those prescribed by the manufacturers;
  • Assess immunogenicity – the ability to produce antibodies and T-cells and B-cells as part of the immune response to the vaccine. These studies looked at the levels of antibodies produced, their effect on neutralizing the virus, how immune responses change over time, which immune responses are most important for protection, and whether exposure to other human seasonal coronaviruses can impact immunity to SARS-CoV-2, among other topics.

Phase 3

Phase 3 began in July 2021 with studies aiming to:

  • Understand the need for booster shots, or third, fourth and subsequent doses, including with bivalent vaccines, in the general population and in specific sub-groups such as long-term care residents, racialized communities, Indigenous Peoples, and people at higher risk due to health conditions or compromised immune systems;
  • Inform the roll out of pediatric vaccines and pediatric booster shots in terms of their safety, effectiveness and immunogenicity;
  • Model trends in aggregate immunity arising from infection and vaccination across Canada to guide public health decision making; and
  • Address cross-cutting issues such as generating comparable measures of immunity across study sites, developing a greater understanding of the immune correlates of protection including regarding hybrid immunity, and improving data sharing across studies and provincial/territorial jurisdictions.

Phase 4

Planning for the final phase of the CITF leading to a revised scientific and operational strategy, occurred in fall 2022. Executive Committee members and Working Party Leads provided inputs in close partnership with the Public Health Agency of Canada (PHAC). Key scientific and administrative areas of focus during the final year of CITF operations were identified as:

  • The full implementation of ongoing studies, including those focused on hybrid immunity and bivalent vaccines, as well as Pediatric Network studies;
  • Data stewardship and the launch of the CITF Databank;
  • Continued serosurveillance modelling and data synthesis work;
  • An assessment of lessons learned (scientific and administrative) throughout the mandate of the CITF;
  • Continued knowledge mobilization focused on the dissemination of funded study results and of the above lessons learned assessment.
  • Sustainability planning and appropriate transition of legacy infrastructures to PHAC or other partners.

Learn more about our funded research

Guiding principles

The COVID-19 Immunity Task Force embraced the following principles and practices:

  1. Partner in all of its work with the Government of Canada and provincial/territorial governments and their agencies, as well as the research community, public health and healthcare professionals/institutions, and a range of community groups.
  2. Establish an ethos in which the rigorous gathering and rapid sharing of data to inform Canadians and to advance the broad public interest over-rides any considerations of personal/group advancement.
  3. Mobilize the best science and study designs that are responsive to the rapidly evolving state of the science related to COVID-19 immunity.
  4. Establish fair and transparent processes consistent with principles of equity, diversity, and inclusion (EDI) that offer all interested partners across the country an opportunity to participate in the CITF, while appropriately managing conflicts of interest.
  5. Work with partners to ensure protection of privacy in data-gathering and safe handling of any and all biological samples.
  6. Collaborate with partners and use existing data- and sample-gathering capacity wherever possible to enhance cost-efficiencies and avoid unnecessary duplication.
  7. Provide a central coordination for the Task Force within a Secretariat that facilitates rapid development of studies, their effective implementation, and rapid reporting of results to key audiences, including decision makers and interested stakeholders, and the broad Canadian public.
  8. Promote ethical and sound participatory practices that engage relevant stakeholders from study design through to dissemination and application of findings.
  9. Adhere to best practices regarding any authorship of scientific publications eventually arising from this work, while ensuring that all participants understand that this work is in the public interest, requiring rapid dissemination of reliable and relevant results.
  10. Liaise with relevant entities in other countries and with international agencies involved in serologic surveys and studies to understand immunity related to SARS-CoV-2.
  11. Communicate the leadership, membership, activities and results of the Task Force with openness and transparency.