The Western Australian experience of COVID-19 after the borders reopened: evaluation of public health modelling predictions

Background: Western Australia (WA) serves as a unique global case study on the impact of coronavirus disease 2019 (COVID-19) on an isolated, prepared and highly vaccinated population. This study builds upon the study performed by House et al. through an extended data set.Aim: To examine the impact of COVID-19 at the only quaternary hospital in WA following the border opening from 3 March to 17 July 2022.Participants: A total of 257 adults were admitted with COVID-19 under either respiratory or the intensive care unit (ICU).Outcomes: Admission numbers, disease severity, ICU admission, prevalence of COVID-19 deterioration risk factors, length of stay and mortality.Results: A total of 257 patients were admitted with COVID-19, under respiratory (81.7%) and ICU (18.3%). COVID-19 was the primary reason for admission for 67.7%. Ten patients died during the study, with seven deaths attributed to COVID pneumonitis. COVID-19 severity was 37.4% mild, 37.0% moderate, 18.3% severe and 7.4% critical. Risk factors for requiring ICU included incomplete immunisation status (P = 0.011), chronic kidney disease (P = 0.008) and Aboriginal and Torres Strait Islander (ATSI) ethnicity. The WA Department of Health predicted that the number of hospitalisations and ICU cases were significantly higher than the actual number of cases.Conclusion: The number of hospitalisations and ICU COVID-19 cases were significantly less than predicted, likely due to high population vaccination rates prior to border opening. The main risk factors for COVID-19 severity were incomplete immunisation and ATSI ethnicity.