Estimation of SARS-CoV-2 Infection Fatality Rate by Real-Time Antibody Screening of Blood Donors

Epidemiology InfectiologyVirology
Erikstrup C et al
Clin Infect Dis

Main result

20,640 blood donors have been informed and have all consented to testing.

After adjusting for assay sensitivity and specificity including their confidence interval (CI), the overall seroprevalence was 1.9% (CI: 0.8-2.3) and differed across areas.

As of May 3, 2020, 484 individuals are reported to have died from SARS-CoV-2 in Denmark; 65 of these were younger than 70. Thus, the combined infection fatality rate (IFR) in patients younger than 70 was estimated at 89 per 100,000 infections (CI: 72-211).


The infection fatality rate was estimated to be slightly lower than previously reported from other countries not using seroprevalence data. The infection fatality rate is likely several fold lower than the current estimate.

The real-time nationwide anti-SARS-CoV-2 seroprevalence surveying of blood donations can be used as a tool in monitoring the epidemic.

Strength of evidence Weak

- Descriptive study.
- Test sensitivity of 82.6%.
- This study only concerns people aged 17 to 69 years old.
- Inter-observer variations for rapid tests.
- uncertainty regarding cross reactivity of SARS-CoV-2 and other coronavirus antibodies.


To conduct a seroprevalence survey among blood donors as a surveillance tool for the SARS-CoV-2 epidemic.


All Danish blood donation facilities participated in this survey. Danish blood donors aged 17–69 years giving blood between April 6 and May 3 were tested for SARS-CoV-2 immunoglobulin M and G antibodies using a commercial lateral flow test. Antibody status was compared between geographical areas and an estimate of the infection fatality rate was calculated. The seroprevalence was adjusted for assay sensitivity and specificity taking the uncertainties of the test validation into account when reporting the 95% confidence intervals (CI).

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