Population Immunity to Influenza and the Risk of Emergence of a Pandemic Virus

Population immunity is a determining factor in relation to the spread of various variants of the influenza virus, and therefore is of great importance for predicting epidemics, characterizing the epidemic process and assessing the effectiveness of vaccination campaigns. The aim of the work was to monitor markers of seasonal influenza viruses and avian influenza viruses in the blood serum of residents of the Russian Federation in 2023–2024. Materials and methods . Blood serum samples from healthy donors were collected in the Siberian Federal District of the Russian Federation in October-November 2023. In addition, blood sera from people who had had contact with sick and/or dead birds and from residents of regions located on migration routes of wild waterfowl were studied in HI-test (hemagglutination inhibition) and virus neutralization. Results and discussion . It is shown that ahead of the epidemic season of 2023/2024, population immunity to influenza in the Siberian Federal District was at the level recommended by the World Health Organization (WHO) – at least 50 % of the immune population. However, among individuals who had had contact with sick and/or dead birds, humoral immunity to seasonal influenza was significantly lower – from 5 % to 30 % seropositive, depending on the region. HI-test on avian influenza viruses A/H5Nx and A/H9N2 has revealed 0 and 3.7 % of positive samples, respectively. The risk of a pandemic influenza virus emergence can be reduced by 75–100 % vaccination against seasonal influenza and monitoring antibody levels in poultry farm workers and employees of other organizations directly involved in poultry breeding and processing.