Grade 1: asymptomatic; clinical or diagnostic observations only; intervention not indicated

Grade 2: symptomatic; medical intervention indicated; limiting instrumental activities of daily living

Grade 3: severe symptoms; limiting self care activities of daily living; oxygen indicated

Grade 4: life-threatening respiratory compromise; urgent intervention indicated (e.g. tracheotomy or intubation)

Reference: Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0 Published: November 27, 2017