The emergence of the COVID-19 pandemic resulted in a dramatic increase in acutely ill patients presenting to hospitals with life-threatening acute respiratory disease. There was an immediate need for effective triage systems to facilitate clinical decision making. This review assesses the performance of the National Early Warning Score 2 (NEWS2) in two contexts. Firstly, the ability to detect acute illness severity and likely clinical deterioration in patients presenting to hospitals with COVID-19. Secondly, the use of NEWS2 in the longitudinal monitoring to detect acute clinical deterioration in hospitalised patients with COVID-19. NEWS2 appeared to be at least comparable and, often, superior to other scoring systems (such as qSOFA and CURB-65), and provided an earlier alert of deterioration. A NEWS2 of 5 had high short-term sensitivity within and was unlikely to miss patients with COVID-19 who go on to deteriorate, but this comes with moderate specificity. However, the specificity of these systems is likely underestimated because preventing deterioration is their purpose. NEWS2 is an adjunct to clinical decision making and has served that purpose during the COVID-19 pandemic, playing an important role in communicating illness severity, clinical deterioration, triaging patients to appropriate levels of care and prompting completion of treatment escalation plans for those with high scores and at imminent risk of deterioration.