The evolution of workplace risk for Covid-19 in Canadian healthcare workers and its relation to vaccination: A nested case-referent study.

BACKGROUND: During the early months of the Covid-19 pandemic, studies demonstrated that healthcare workers (HCWs) were at increased risk of infection. Few modifiable risks were identified. It is largely unknown how these evolved over time. METHODS: A prospective case-referent study was established and nested within a cohort study of Canadian HCWs. Cases of Covid-19, confirmed by polymerase chain reaction, were matched with up to four referents on job, province, gender, and date of first vaccination. Cases and referents completed a questionnaire reporting exposures and experiences in the 21 days before case date. Participants were recruited from October 2020 to March 2022. Workplace factors were examined by mixed-effects logistic regression allowing for competing exposures. A sensitivity analysis was limited to those for whom family/community transmission seemed unlikely. RESULTS: 533 cases were matched with 1697 referents. Among unvaccinated HCWs, the risk of infection was increased if they worked hands-on with patients with Covid-19, on a ward designated for care of infected patients, or handled objects used by infected patients. Sensitivity analysis identified work in residential institutions and geriatric wards as high risk for unvaccinated HCWs. Later, with almost universal HCW vaccination, risk from working with infected patients was much reduced but cases were more likely than referents to report being unable to access an N95 mask or that decontaminated N95 masks were reused. CONCLUSIONS: These results suggest that, after a rocky start, the risks of Covid-19 infection from work in health care are now largely contained in Canada but with need for continued vigilance.

The Health of Firefighters Deployed to the Fort McMurray Fire: Lessons Learnt.

Introduction: Firefighters were working in exceptionally difficult conditions during the Fort McMurray/Horse River fire in May 2016. Methods: From mid-May, we recruited firefighters from 13 fire services as they returned from the fire. In October 2016 we extended recruitment to all Alberta-based firefighters deployed to the fire. In December 2017-May 2018 we sent a first online follow-up: this concentrated on mental health supports. The second follow-up, in October 2018-January 2019, included screening scales for respiratory ill-health and PTSD. All three contacts included visual analogue scales for chest symptoms and the Hospital Anxiety and Depression Scale. We estimated exposure to PM2.5, and calculated an exposure mitigation index from reports of respiratory protective equipment (RPE). Results: We recruited 1,234 firefighters and examined the relation of respiratory symptoms to estimated particulate exposure. The relation was strong immediately post fire but weakened over time. We found less chest tightness and cough in those whose RPE in the first week mitigated exposure by at least 10%. We examined the relation between particulate exposure and mental ill-health from screening questionnaires and found those with high exposure (reflecting the ferocity of the fire) had poorer mental health scores. Firefighters reporting their "worst moment during the fire" was life threatening were more anxious at second follow-up. Overall both anxiety and depression scores increased at successive contacts, more so in those with mental ill-health recorded in physician billing records before the fire. Discussion: The results from this study overall suggest on-going fire-related health effects in a substantial minority of firefighters, similar to those reported in the longitudinal follow-up of firefighters after the collapse of the World Trade Centre. Self-reports of both respiratory symptoms and mental ill-health were strongly related, soon after the fire, to estimated particulate exposures. Anxiety increased over time since the fire in those who felt their life or safety had been threatened, underlining the need for ongoing support. Our conclusions about the benefits of rapid research relate particularly to the collection of biomarkers of exposure as quickly and widely as possible, and the establishment of a nominal list of participants before they are too widely dispersed.

COVID-19 infection and mental wellness in a Canadian cohort study of healthcare workers

IntroductionHealthcare workers (HCW) working through the pandemic are in the front line for infection, psychological pressure and overwork.ObjectivesTo identify modifiable work factors associated with COVID-19 infection and mental distress, and to assess the effectiveness of provisions to mitigate their impact.MethodsA cohort study of HCWs was set up in the first weeks of the pandemic in Canada. HCWs from British Columbia, Alberta, Ontario, and Quebec completed an online questionnaire in the spring/summer of 2020, and a Phase 2 questionnaire from October 2020. They also provided a blood sample to assess SARS-CoV-2 antibodies. HCWs reporting a COVID-19 infection after the Phase 2 questionnaire were matched on job-type and province to 4 referents for a nested case-referent (C-R) study concentrating on exposures immediately prior to infection. Phase 3 is underway, with a final contact planned for March 2022.Results5135 HCWs completed the Phase 1 questionnaire with 93% (4539/4857) of those eligible completing Phase 2. By March 1st 2021, 157 cases had been confirmed by PCR and a further 10 found positive only on antibody testing (an overall rate of 3.3%). The odds of infection doubled for working one-on-one with known COVID-19 patients. Rates were lower in physicians and nurses, compared to personal support workers, health care aides, and licensed practical nurses. HCWs in a hospital setting had lower rates than those working in the community, where shortages of personal protective equipment were more widespread. High rates of anxiety (on the Hospital Anxiety and Depression Scale) were recorded in both Phase 1 and 2. Only 1 in 4 HCW had used available mental health supports. By May 2021, 100 cases with 389 referents had been recruited to the on-going C-R study.ConclusionInformation collected prospectively has the potential to improve HCWs protection during this and future epidemics.