Understanding and Interpretation of Case Fatality Rate of Coronavirus Disease 2019

Kim, Dong-Hyun; Choe, Young June; Jeong, Jin-Young

Lastly, CFR should be interpreted cautiously given the time difference between disease onset and death. Fatal cases used to be ascertained as COVID-19 cases much earlier, and thus the denominator of the fatality rate should be the total number of cases confirmed at the same time as those who died in the numerator. That is, the denominator and the numerator of CFR should be composed of patients infected at the same time as those who died in order to accurately represent the actual CFR. 6 Most of the recently diagnosed patients in many countries are still likely to be in the care-state. That is, the cross-sectional comparison of these figures may be biased since the time span for illness is different among countries during the course of the ongoing epidemic. To avoid this bias, time-delay adjusted estimates between symptom onset and death need to be calculated for a fair comparison of CFRs among different countries. 7 Russell et al. 8 proposed a delay-adjusted CFR to correct the delay between confirmation-and-death, using the distribution of the delay from hospitalization-todeath for cases that are fatal from Wuhan, China.