Estimation of SARS-CoV-2 Infection Fatality Rate by Age and Comorbidity Status Using Antibody Screening of Blood Donors During the COVID-19 Epidemic in Denmark

Background. Studies presenting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection fatality rate (IFR) for healthy individuals are warranted. We estimate IFR by age and comorbidity status using data from a large serosurvey among Danish blood donors and nationwide data on coronavirus disease 2019 (COVID-19) mortality. Methods. Danish blood donors aged 17-69 years donating blood October 2020-February 2021 were tested with a commercial SARS-CoV-2 total antibody assay. IFR was estimated for weeks 11 to 42, 2020 and week 43, 2020 to week 6, 2021, representing the first 2 waves of COVID-19 epidemic in Denmark. Results. In total, 84 944 blood donors were tested for antibodies. The seroprevalence was 2% in October 2020 and 7% in February 2021. Among 3 898 039 Danish residents aged 17-69 years, 249 deaths were recorded. The IFR was low for people < 51 years without comorbidity during the 2 waves (combined IFR = 3.36 per 100 000 infections). The IFR was below 3 parts per thousand for people aged 61-69 years without comorbidity. IFR increased with age and comorbidity but declined from the first to second wave. Conclusions. In this nationwide study, the IFR was very low among people < 51 years without comorbidity.

Automated summary

The study shows that the infection fatality rate (IFR) of healthy individuals under 51 years old without comorbidities is very low. However, the IFR increases with age and comorbidity. Additionally, there was a decline in IFR from the first to the second wave of the epidemic.