Changing case fatality risk for COVID-19 over time in selected European countries
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Abstract
Objectives To illustrate the development of the case fatality risk (CFR) for COVID-19 over time using different assumptions for calculating the CFR. Design Observational study. Setting Selected European countries, 28 January to October 29 2020. Participants Laboratory-confirmed COVID-19 cases and deaths due to COVID-19 Main outcome measure case fatality risk (CFR) Results We show that the CFR has considerably decreased over time. This seems to be driven not only by increased testing but also by a reduced CFR among cases older than 60 years. Our data also confirm a significantly higher fatality risk for men than for women. The decline in the CFR is even more pronounced when only cases and deaths occurring in a specified time window are considered. This alternative estimation method has the advantage that early data where the bias due to the incomplete ascertainment of cases was arguably largest do not affect CFR estimates later on. We find similar results for other European countries. Conclusion CFR estimates vary considerably depending on the underlying assumptions concerning their calculation. Reliable CFR estimates should not be based on cumulative numbers from the beginning of the pandemic but rather be based on more recent data only.
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SciScore for 10.1101/2020.11.26.20239327: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Our estimation methods included some assumptions as well as limitations. We aimed to keep the calculations simple using a fixed time from reporting to death. The distribution and its mean may have changed over time towards a …
SciScore for 10.1101/2020.11.26.20239327: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Our estimation methods included some assumptions as well as limitations. We aimed to keep the calculations simple using a fixed time from reporting to death. The distribution and its mean may have changed over time towards a shorter interval from infection to reporting. In a period with daily rising numbers, such as in the second half of October, the age-standardized CFR estimate is notably higher when assuming 14 days rather than 7 days. It is possible that a time of 7 days may be too short, which would yield to an underestimation of the CFR when the case numbers are quickly rising. Until mid-October the differences in the CFR estimates with lag 14 or 7 days are small, as shown in the results, and these estimates appear to be robust. The time window of 2 months has been chosen arbitrarily. We selected an interval which is long enough to accumulate sufficient numbers for a stable estimation, and short enough to show changes over time clearly. We checked other intervals (one and three months) and found very similar results. In conclusion, we have suggested an estimate of the CFR of COVID-19 which is based on more recent data only. We recommend not to calculate CRF based on cumulative numbers from the beginning of the pandemic. We showed a decrease of the CFR of COVID-19 over time.
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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SciScore for 10.1101/2020.11.26.20239327: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
Our estimation methods included some assumptions as well as limitations. We aimed to keep the calculations simple using a fixed time from reporting to death. The distribution and its mean may have changed over time towards a shorter interval from infection to reporting. In a period with daily rising numbers, such as in the second half …
SciScore for 10.1101/2020.11.26.20239327: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
Our estimation methods included some assumptions as well as limitations. We aimed to keep the calculations simple using a fixed time from reporting to death. The distribution and its mean may have changed over time towards a shorter interval from infection to reporting. In a period with daily rising numbers, such as in the second half of October, the age-standardized CFR estimate is notably higher when assuming 14 days rather than 7 days. It is possible that a time of 7 days may be too short, which would yield to an underestimation of the CFR when the case numbers are quickly rising. Until mid-October the differences in the CFR estimates with lag 14 or 7 days are small, as shown in the results, and these estimates appear to be robust. The time window of 2 months has been chosen arbitrarily. We selected an interval which is long enough to accumulate sufficient numbers for a stable estimation, and short enough to show changes over time clearly. We checked other intervals (one and three months) and found very similar results. In conclusion, we have suggested an estimate of the CFR of COVID-19 which is based on more recent data only. We recommend not to calculate CRF based on cumulative numbers from the beginning of the pandemic. We showed a decrease of the CFR of COVID-19 over time. Article Summary Strengths and limitations of this study • New aspects of estimation of the case fatality risk (CFR) have been investigated • It has been shown that the CFR decreased over time • The c...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
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