The ‘relative severity ratio’ compares COVID-19 mortality to the pre-pandemic mortality profile of individual countries. This involves two comparisons. The first comparison is made through the severity ratio itself, which compares COVID-19 mortality with all-cause mortality in 2019. The second one is the comparison of the severity ratio with cause-specific proportionate mortality rates (the share of deaths due to a specific cause in total deaths).
These comparisons are useful as the expression of mortality in relative terms speaks to the fact that countries may have adapted to their specific patterns of mortality. Deviations from this pattern may create pressure points, such as, for example, on the health system. Comparisons with previous patterns give a country-specific flavor of the severity of the COVID-19 pandemic, which could be used to corroborate realities on the ground.
Comparisons with top causes of death are with reference to the 133 disease families of the 2019 Global Burden of Disease study (at the third level of ICD-10). We select the top nth cause of death, which most closely approximates the peak COVID-19 severity ratio from below. More details on the concept of relative severity are in the paper of Schellekens and Sourrouille (2020) that developed the concept, which can found here.
Source: World Bank