The role of genetic variants of the SARS-CoV-2 virus in forming of intra-annual increases in the incidence of COVID-19 in Perm Region

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BACKGROUND: The causes of intra-annual increases in COVID-19 incidence remain insufficiently studied.
 AIM: This study aimed to investigate the role of genetic variants of SARS-CoV-2 in intra-annual increases of COVID-19 incidence in the Perm region.
 MATERIALS AND METHODS: The monthly dynamics of COVID-19 morbidity and mortality of the population of the Perm region from March 2020 to December 31, 2022 was assessed. The analysis of the monthly frequency of isolation of patients with different genetic variants of SARS-CoV-2 was conducted based on the study results of 2,592 samples from patients in the Perm region performed by specialized laboratories of research institutes in Russia between March 2021 and December 2022. The assessment of the incidence of IgG antibodies to coronavirus among the population was provided according to blood serum studies of 14,006 people.
 RESULTS: In 2020–2022, 4 rises in the incidence of COVID-19 were detected in the Perm region against the background of the emergence of new genetic variants of the pathogen, mainly Alpha, Delta, and Omicron. Increases in COVID-19 incidence and a change in the genetic structure of the pathogen were observed despite an increase in the proportion of people with SARS-CoV-2 IgG in the blood serum. Against the background of the third and fourth increases in morbidity, when the Omicron genotype acquired the leading etiological significance, the infection fatality rate decreased significantly.
 CONCLUSIONS: Intra-annual increases in COVID-19 incidence are largely associated with changes in the genetic structure of the pathogen and are observed despite an increase in the number of people among the population with IgG to SARS-CoV-2 in the blood serum.