ABSTRACT
Recent evidence showed greater efficacy of tocilizumab (TCZ) in the subgroups of COVID-19 patients who presented with symptoms for less than 7 days and in those only receiving oxygen. We retrospectively analyzed a compassionate use cohort to determine the best timing for TCZ injection. We showed no association between the timing of injection after symptom onset and the efficacy of TCZ on mortality. We then investigated whether the oxygen level at the time of TCZ injection impacted the mortality rate. Our study finally suggested that TCZ could be less effective when oxygen requirement is >11L/min and we hypothesized that earlier administration could be associated with better outcome. However, randomized clinical trials are required to confirm this hypothesis.