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.