Long-term detection of SARS-CoV-2 antibodies after infection and risk of re-infection
Bo Langhoff Hønge, Lotte Hindhede, Kathrine Agergård Kaspersen, Lene Holm Harritshøj, Susan Mikkelsen, Dorte Kinggaard Holm, Anna Christine Nilsson, Susanne Gjørup Sækmose, Erik Sørensen, Bitten Aagaard, Henrik Hjalgrim, Charlotte Sværke Jørgensen, Tyra Grove Krause, Henrik Ullum, Ole Birger Pedersen, Sisse Rye Ostrowski, Christian Erikstrup
Abstract
OBJECTIVES: To evaluate long-term sensitivity for detection of total antibodies against SARS-CoV-2 METHODS: From week 41, 2020, through week 26, 2021, all Danish blood donations were tested for SARS-CoV-2 antibodies with the Wantai assay. The results were linked with polymerase chain reaction (PCR) test results from the Danish Microbiological Database (MiBa). RESULTS: During the study period, 105,646 non-vaccinated Danish blood donors were tested for SARS-CoV-2 antibodies, and 3,806 (3.6%) had a positive PCR test before the blood donation. Among the donors with a positive PCR test, 94.2% subsequently also had a positive antibody test. The time between the positive PCR test and the antibody test was up to 15 months and there was no evidence of a decline in proportion with detectable antibodies over time. A negative serological result test was associated with a higher incidence of re-infection (Incidence Rate Ratio = 0.102 (95% confidence interval (CI): 0.039-0.262)). CONCLUSION: Among healthy blood donors, 94.2% developed SARS-CoV-2 antibodies after infection, and a lack of detectable antibodies was associated with re-infection.