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Differences in case-fatality-rate of emerging SARS-CoV-2 variants
Jing Liu1, Haozhen Wei1, Daihai He1,2
1Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China.
Public Health in Practice (Oxford, England)
|December 19, 2022
Summary
The Case-Fatality-Rate (CFR) for SARS-CoV-2 variants significantly dropped, especially from Delta to Omicron, likely due to increased population immunity. Omicron subvariants showed similar severity.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Severe-Acute-Respiratory-Syndrome Coronavirus-2 (SARS-CoV-2) variants have caused global impact.
- Omicron (B.1.1.529) appears less deadly than Delta (B.1.617.2), attributed to immunity from vaccination and prior infection.
- Case-Fatality-Rate (CFR) is a key metric for variant severity.
Purpose of the Study:
- To calculate the change in CFR for different SARS-CoV-2 variants over time.
- To analyze variant severity across numerous countries/regions since the pandemic's start in 2020.
Main Methods:
- A cross-sectional study design was employed.
- Comparison extended to all previous Variants of Concern (VOCs) in 58 countries/regions.
- CFR calculated using reported deaths divided by reported cases within a 30-day sliding window with a two-week lag.
Main Results:
- A substantial drop in CFR was observed from the Delta variant to the Omicron variant.
- No significant difference in CFR was evident between Omicron subvariants.
- CFR generally decreased over time across variants.
Conclusions:
- The decline in CFR is likely due to vaccine-induced and infection-induced immunity.
- Population demographics, including age structure and comorbidity prevalence, influence CFR.
- Continued monitoring of variant severity is crucial for public health strategies.
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