Cherry Nicola, Mhonde Trish, Adisesh Anil, Burstyn Igor, Durand-Moreau Quentin, Labrèche France, Ruzycki Shannon
Division of Preventive Medicine, University of Alberta, Edmonton, Alberta, Canada.
Division of Occupational Medicine, University of Toronto, Toronto, Ontario, Canada.
Am J Ind Med. 2023 Apr;66(4):297-306. doi: 10.1002/ajim.23466. Epub 2023 Feb 3.
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.
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.
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.
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.
在新冠疫情的最初几个月，研究表明医护人员感染风险增加。几乎没有发现可改变的风险因素。这些风险因素如何随时间演变在很大程度上尚不清楚。
开展了一项前瞻性病例对照研究，并嵌套于一项针对加拿大医护人员的队列研究中。经聚合酶链反应确诊的新冠病例与最多四名对照者在工作岗位、省份、性别和首次接种日期方面进行匹配。病例和对照者完成一份问卷，报告病例确诊日期前21天的暴露情况和经历。研究对象于2020年10月至2022年3月招募。通过混合效应逻辑回归分析工作场所因素，并考虑竞争性暴露。敏感性分析仅限于那些家庭/社区传播可能性不大的人群。
533例病例与1697名对照者匹配。在未接种疫苗的医护人员中，如果他们直接接触新冠患者、在指定用于护理感染患者的病房工作或处理感染患者使用过的物品，感染风险会增加。敏感性分析确定在住宿机构和老年病房工作对未接种疫苗的医护人员来说是高风险。后来，随着医护人员几乎普遍接种疫苗，与感染患者接触的风险大幅降低，但病例比对照者更有可能报告无法获得N95口罩或使用过经过消毒的N95口罩。
这些结果表明，在经历了艰难的开端后，加拿大医疗保健工作中新冠感染的风险目前在很大程度上已得到控制，但仍需持续保持警惕。
