This is a summary, written by members of the CITF Secretariat, of:

Cherry N, Mhonde T, Adisesh A, Burstyn I, Durand-Moreau Q, Labrèche F, Ruzycki S. The evolution of workplace risk for Covid-19 in Canadian healthcare workers and its relation to vaccination: A nested case-referent study. Am J Ind Med. 2023 Feb 3. doi: https://doi.org/10.1002/ajim.23466.

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study published in the American Journal of Industrial Medicine looked at the risk of infection among healthcare workers (HCW). It found that unvaccinated HCW who came into direct contact with patients with COVID-19 on a ward designated for care of infected patients, or who handled objects used by infected patients were at elevated risk. Once vaccination became almost universal among HCWs, the risk from working with infected patients was much reduced but remained higher for vaccinated HCWs without access to N95 masks or who reused masks. This study was led by Dr. Nicola Cherry (University of Alberta).

Key findings:

  • Among unvaccinated HCWs (defined as those with one or no vaccine doses), the risk of getting COVID‐19 increased in those working with patients known or suspected of having COVID‐19 (odds ratioAn odds ratio of 1.0 indicates that the odds of exposure among case-patients are the same as, or similar to, the odds of exposure among controls. The exposure is not associated with the disease.
    An odds ratio of greater than 1.0 indicates that the odds of exposure among case-patients are greater than the odds of exposure among controls. The exposure might be a risk factor for the disease.
    An odds ratio of less than 1.0 indicates that the odds of exposure among case-patients are lower than the odds of exposure among controls. The exposure might be a protective factor against the disease.
     [OR] = 2.62); working on wards designated for the care of infected patients (OR = 4.75); or handling objects, outside of clinical care, such as trays or bedding used by patients with COVID‐19 (OR = 2.03).
  • Vaccinated HCW (defined as those with two or more doses) who came in contact with COVID-19 infected patients had an elevated estimated risk of infection (OR = 1.74), but this was half that of the unvaccinated HCWs (OR=3.51).
  • Unvaccinated HCWs were at greater risk if they worked in residential institutions (OR = 2.42) or in geriatric wards (OR = 3.97).

This study highlights that HCWs were at risk of infection through their workplace early in pandemic when there were few protective health measures in place and before vaccination was available. Now, the risks of infection have been reduced due to the infection control measures in workplaces and vaccination of patients and co-workers.

Participants were recruited from April-October 2020 and followed up to September 2022. The introduction of vaccines in December 2020 provided the opportunity to assess the changing pattern of workplace risks for those receiving at least two doses of vaccine.