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COVID-19 Cohort Study for People Working in Healthcare (CCS)

COVID-19 Cohort Study for People Working in Healthcare (CCS)

(attribution Image by on Freepik)

Status: Data collection complete, analysis ongoing Study Results French site

What was the purpose of this study?

The COVID-19 Cohort Study (CCS) and the Canadian CCS (CCCS) were prospective cohort studies that collected data from June 2020 to December 2023 in collaboration with Canadians who work in healthcare. The primary objectives were to determine the rate of COVID-19 infection, changes in antibody levels over time, the impact of vaccines against COVID-19, and the psychological impact of working during a pandemic.

Study design Number of sites Number of participants Study period
Prospective Cohort Study 19 3435 June 2020 – December 2023

Who was eligible to participate?

People working in acute care, rehabilitation, or complex care hospital who:
  • Were 18 to 75 years old
  • Worked anywhere in a participating hospital for ≥20 hours per week; was a MD/NP with privileges who spent ≥8 hours per week in the hospital

People who worked in private medical practice in the Toronto area.

In the Toronto and Hamilton areas, household members of study participants were also eligible to participate.

What data was collected?

  • Respiratory illness information, with COVID-19 test results
  • Risk factors for testing positive for SARS-CoV-2 (personal, household, workplace, and community)
  • Blood samples to detect cases of asymptomatic or undiagnosed COVID-19 and changes in antibody levels (over time, after vaccinations and illnesses)
  • Levels of distress while working during the COVID-19 pandemic
  • Attitudes regarding COVID-19 vaccination

Who funded this study?


Research sites and investigators

  Participating sites Investigators
Toronto  & area Oak Valley Health Dr. Jeya Nadarajah
Michael Garron Dr. Jeff Powis & Dr. Chris Kandel
North York General Dr. Kevin Katz
Private MD, NP, or midwifery clinics/practices in the GTA Dr. Brenda Coleman
Sinai Health Dr. Allison McGeer & Dr. Brenda Coleman
Sunnybrook Health Sciences Centre Dr. Samira Mubareka
Unity Health (St. Michael’s site) Dr. Matthew Muller
University Health Network Dr. Allison McGeer
William Osler Health System Dr. Saranya Arnoldo
Hamilton Hamilton Health Sciences Dr. Mark Loeb
St. Joseph’s Healthcare Hamilton Dr. Marek Smieja
Ottawa Ottawa Dr. Curtis Cooper
Calgary Calgary Health Zone Dr. Robyn Harrison
Edmonton Grey Nuns Community Hospital (Edmonton) Dr. Robyn Harrison
University of Alberta Hospital Dr. Robyn Harrison
Royal Alexandra Hospital Dr. Robyn Harrison
Nova Scotia
  IWK Health Dr. Joanne Langley
Nova Scotia Health Dr. Shelly McNeil
  Sherbrooke Dr. Louis Valiquette

with the invaluable assistance of our staff: Sarah, Julia, Ajibola, Ayo, Susan, Angel, Max, Iris, Kanchan, Nicole, Veronica, Chloe, Simon, & TJ.


The study investigators and everyone who worked on the CCS would like to sincerely thank all participants for the time and effort they put into helping us collect data about their experiences during the last 3½ years of the SARS-CoV-2 / COVID-19 pandemic. We cannot adequately express our gratitude.

Thank you

(attribution Image by Freepik)

Contact us

If you have questions, please contact Toronto Invasive Bacterial Diseases Network.