Formation of collective immunity against a new coronavirus infection COVID-19 in blood donors

Introduction. The new coronavirus infection COVID-19, fi rst detected at the end of 2019 in the Chinese city of Wuhan, caused a worldwide pandemic. High mortality among people with chronic diseases, a high frequency of the severe form of the disease, and an unspecifi ed number of asymptomatic carriers are all causes for heavy burden on the healthcare system, including the blood bank service.Aim – to assess the SARS-CoV-2 antibody formation in blood donors.Materials and methods. The research included test results for 12,314 blood samples of donors who donated blood during 04.29.2020 – 08.04.2021 at the National Medical Research Center for Hematology (Russia). Anti-RBD-SARS IgG were tested by «SARS-CoV-2-IgG-ELISA», manufactured by the National Medical Research Center for Hematology, LLC «HEMA» (Russia).Results. Among 12,314 blood samples from donors, 3,219 (26.14 %) were positive for antibodies to SARS-CoV-2. Antibodies detection rate increased from 8.52 to 58.09 % during the observation period. For representative evaluation of donors’ anti-SARS antibodies growth profi le, the results of detection were analyzed within two-week periods (including holidays). This approach made it possible to avoid counting the same donor twice. In the profi le of the growth of collective immunity in donors, two periods were identifi ed: May – November 2020 and November 2020 – April 2021. The period of May – November 2020 proved no signifi cant change in antibodies detection in donors. Detection rate was stable at about 15 % (13.10–16.24 %). The second period, from November 2020 to April 2021, demonstrated sustainable growth of this parameter from 16.20 to 58.09 %. This is likely due to the start of the second wave of COVID-19 in Russia (starting from November 2020) and an active campaign for mass vaccination that started in December 2020. To assess the true rate of increase of specifi c immunity in donors, the frequency of primary detection of antibodies to SARS-CoV-2 in donors in relation to those donors in whom antibodies were detected earlier was analyzed. The contribution of cases of primary detection of antibodies to SARS-CoV-2 was wave-like and corresponded to the epidemiological situation.Conclusion. An increase in the frequency of detection of antiviral antibodies in gratuitous blood donors was found during the spread of the second wave of COVID-19 and the n the beginning of mass vaccination. The increase in the overall frequency of antibody detection was due to donors with newly and re-detected antibodies. The surge in the frequency of primary detection of antibodies in blood donors corresponded to the second wave of infection.