Estimating COVID-19 Case Fatality Rate in the Middle of the Outbreak: Deadlier than Previously Estimated
19 Pages Posted: 30 Mar 2020More...
Background: During the ongoing COVID-19 outbreak, the public are concerned about the case-fatality rate (CFR) of COVID-19. Previously reported CFR values vary widely from 0.4% to 15%. The method used in previous studies to estimate CFR during the epidemic is also questionable.
Methods: Data for this study were from the National Health Commission of China from mid-January until March 11, 2020 with 80,793 COVID-19 cases and 3,169 deaths. We applied the commonly used binomial probability method and a survival analysis method to estimate CFR values at different time points for China and China outside of Hubei.
Findings: Death rates decreased over time during the epidemic. By March 11, 2020, the COVID-19 death rate had dropped to 13.4 per 10,000 patient-days since diagnosis (95% CI: 12.9, 13.9) in China, and 2.6 per 10,000 patient-days (95% CI: 2.2, 3.2) in China outside of Hubei. The estimated CFR values using the commonly used binomial probability method were much lower than using the survival analysis method, particularly at early time of the epidemic. The survival analysis estimates decreased while the binomial probability estimates increased over time during the epidemic. By March 11, 2020, the binomial probability estimates had reached 3.9% (95% CI: 3.8, 4.1) for China and 0.87% (95% CI: 0.72, 1) for China outside of Hubei, still lower than the corresponding values estimated using the survival analysis method: 4.6% (95% CI: 4.4, 4.7) for China and 0.92% (95% CI: 0.76, 1.1) for China outside of Hubei.
Interpretation: During the epidemic of COVID-19, the previously used binomial probability method not only underestimates the CFR of COVID-19, but also leads to a false increasing trend over time. A survival analysis method is recommended for estimating CFR during the COVID-19 epidemic. The current CFR estimate for China including Hubei is 4.6%, about 5 times the value for China of outside Hubei (0.92%). There has been a CFR decreasing trend during the epidemic.
Funding Statement: This work was funded by the National Natural Science Foundation of China (81573255 to ML).
Declaration of Interests: None.
Keywords: COVID-19; Case fatality rate; novel coronavirus; SARS-CoV-2; Epidemic; Outbreak
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