The ‘relative severity ratio’ compares COVID-19 mortality to the pre-pandemic mortality profile of individual countries. 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 COVID19 pandemic, which could be used to corroborate realities on the ground.
Comparisons with top causes of death are with references 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 mostly closely approximates the peak COVID-19 severity ratio from below. More details on the concept of relative severity can be found here.
Based on the above methodology, we can construct relative severity ratios for aggregated income groups as well. The aggregation involves two steps (corresponding to the two comparisons mentioned earlier). The first one amounts to aggregating all COVID-19 fatalities as well as all-cause fatalities in 2019 for all countries in the group. This yields the relative severity ratio. The second one requires identifying the top causes of death by proportionate mortality rates for the aggregated groups. This requires aggregation of the 133 disease categories and selection of the most prevalent ones at the level of the group.
In the above chart, we show for visualization purposes only the relative severity ratios themselves and not the corresponding top causes (these can be found in individual charts for HICs, UMICs, LMICs and LICs). The chart shows that relative to the pre-pandemic mortality profile HICs have suffered the highest levels of relative severity.The chart confirms the typical mortality patterns across the income classification with severity declining for lower-income countries.
The World Bank has recently launched an interactive tool on its data platform, with which you can calculate the indicator for any country, region or income group. Check out the COVID-19 dashboard on relative severity.