Testing and criteria for diagnosis COVID-19 is likely to rapidly evolve over the course of this trial and will vary internationally. Therefore, the following pragmatic definitions will be applied: Confirmed positive test for COVID-19: either a laboratory test (performed according to each participating hospital’s local protocols) or a computed tomography (CT) thorax scan (based on individual radiologist interpretation and diagnosis) that confirms COVID-19 diagnosis. Confirmed negative test for COVID-19: a laboratory test (performed according to each participating hospital’s local protocols) that is negative for COVID-19 diagnosis. Patients are eligible for the study if ALL of the following apply: -Aged 18 years or above -Planned to undergo any type of elective or emergency inpatient surgery requiring general or regional anaesthesia (such as vulnerable patients undergoing surgery for a fractured neck of femur) -Asymptomatic of COVID-19, including patients with: those not tested, negative test results, postive test but no symptoms -Able to provide informed patient consent The eligibility criteria may change over time to reflect new diagnostic tests or changing epidemiology. This will be reviewed regularly by the Trial Management Group and Data Monitoring Committee. For example, if routine serological screening before surgery becomes feasible during the course of the trial in any participating hospital, only seronegative patients may be eligible for the trial.

Testing and criteria for diagnosis COVID-19 is likely to rapidly evolve over the course of this trial and will vary internationally. Therefore, the following pragmatic definitions will be applied: Confirmed positive test for COVID-19: either a laboratory test (performed according to each participating hospital’s local protocols) or a computed tomography (CT) thorax scan (based on individual radiologist interpretation and diagnosis) that confirms COVID-19 diagnosis. Confirmed negative test for COVID-19: a laboratory test (performed according to each participating hospital’s local protocols) that is negative for COVID-19 diagnosis. Patients are eligible for the study if ALL of the following apply: -Aged 18 years or above -Planned to undergo any type of elective or emergency inpatient surgery requiring general or regional anaesthesia (such as vulnerable patients undergoing surgery for a fractured neck of femur) -Asymptomatic of COVID-19, including patients with: those not tested, negative test results, postive test but no symptoms -Able to provide informed patient consent The eligibility criteria may change over time to reflect new diagnostic tests or changing epidemiology. This will be reviewed regularly by the Trial Management Group and Data Monitoring Committee. For example, if routine serological screening before surgery becomes feasible during the course of the trial in any participating hospital, only seronegative patients may be eligible for the trial.