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.