Implemented on Wednesday, the international system counts a person's age from zero at birth, whereas the abolished traditional systems added one or two years to a person's age, depending on the birth date.
"The tool provides nuanced information on people's risk of serious illness due to Covid-19 and is designed for use by clinicians with patients to reach a shared understanding of risk."
Scientists, including those from Hokkaido University, modelled available data from Japan, Spain and Italy to show that susceptibility to COVID-19 is independent of age.