Examination of factors affecting SARS-CoV-2 transmission among healthcare workers following a large healthcare-associated outbreak of COVID-19 in North West Tasmania

Objectives In March 2020, Australia experienced its first large COVID-19 outbreak in a healthcare setting when two persons who had returned from cruise ship travel were admitted to a hospital in North West Tasmania, leading to sustained severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission among healthcare workers (HCWs) in this hospital and another hospital co-located in the same health precinct. We examined factors influencing SARS-CoV-2 transmission in these hospitals to inform policies and practices that could reduce the risk of future outbreaks. Methods Using the results of a survey and SARS-CoV-2 testing of HCWs who attended work at one or both hospitals during the exposure period (20 March to 13 April 2020), we assessed the association of demographic variables, work-related variables, and the average score for each of three infection prevention and control (IPC) measures (hand hygiene, personal protective equipment [PPE] donning and doffing, and personal distancing) with being a COVID-19 case using logistic regression. Results Of the 1779 HCWs invited to participate in the survey, 410 responded, of which 125 met the inclusion criteria for our analysis. On multivariable regression analysis, HCWs who were aged 31–50 years (odds ratio [OR] = 0.12 [95% confidence interval (CI): 0.03, 0.48]) or 51+ years (OR = 0.17 [95% CI: 0.04, 0.68]) had significantly lower odds of being a COVID-19 case when compared with HCWs who were aged 30 years or less, whereas those who worked part time (OR = 0.29 [95% CI: 0.08, 0.91]) had significantly lower odds of being a COVID-19 case when compared with HCWs who worked full time. HCWs having direct care of a COVID-19-positive patient (OR = 5.42 [95% CI: 1.65, 20.8]) had significantly higher odds of being a COVID-19 case when compared with HCWs without direct care of a COVID-19-positive patient. The IPC measures showed no significant association with COVID-19 case status. Conclusions Our study identified important associations between COVID-19 acquisition and age, work frequency, and direct contact with COVID-19 patients. However, the small sample size of IPC measures meant our study was inadequately powered to determine the significance of these associations with COVID-19 acquisition.