Table 1.

A summary of protocol components for the target trial emulation.

Protocol Component	Description of Emulation
Research questions	Is ‘X’ antiviral treatment associated with lower in-hospital mortality among patients hospitalized with COVID-19? Does the length of in-hospital stay differ between X-treated and non-X-treated patients?
Outcomes	In-hospital death and discharge alive (competing event)
Eligibility criteria	Adult patients aged ≥18 years PCR confirmed SARS-CoV-2 infection or HRCT chest findings Hospitalized within time period from February until May 2020
Exclusions	Any contraindication to ‘X’ antiviral treatment (e.g., liver dysfunction, kidney injury, cardiac arrhythmias, including QT prolongation) at hospital admission that made the patient unsuitable for receiving ‘X’ treatment
Treatment strategies	Initiate ‘X’ treatment (‘treated’) within two days of hospital admission Do not initiate ‘X’ treatment (‘untreated’) within two days of hospital admission
Treatment assignment	Non-randomized ‘X’ treatment assignment
Follow-up time	Begins with hospital admission, and treatment initiation must occur within the first two days after hospitalization and end at 60 days or in-hospital death or discharged alive
Grace period	First two days after hospital admission
Estimand	Difference in the risk for in-hospital death and discharge alive
Analysis plan	●Emulation of target trial: Analysis conducted on the cloned data set assuming random treatment assignment and with a censoring indicator when there is a protocol deviation within the grace period; selection bias accounted for by using inverse probability of artificial censoring weights. ●Type of primary analysis and statistical model: o Cause-specific hazard approach is selected to account for competing risks o Cause-specific discrete time-constant hazards for in-hospital death and discharge alive estimated via weighted pooled logistic regression o Cause-specific cumulative incidences estimated via weighted cumulative incidence functions o Differences in risk for in-hospital death and discharge alive
Adjustment variables	Demographic: age and sex Clinical characteristics: oxygen saturation, respiratory rate, and creatinine serum level measured at hospital admission

Abbreviations: COVID-19, Coronavirus disease 2019; HRCT, high-resolution computed tomography; PCR, polymerase chain reaction.