Characterisation of the COVID-19 Epidemic Process in Moscow and Search for Possible Determinants of the Trends of the Observed Changes

Background. Constant assessment of the dynamics of the main characteristics of the epidemic process is the basic function of epidemiological surveillance of infectious diseases. The search for factors that determine changes in the characteristics of the epidemic process makes it possible to develop timely management decisions and reduce the risk of an increase in the scale of the pandemic. Moscow is the main centre of attraction for the population of other Russian regions with the most complex structure of social links and the highest population density. The purpose of the study is to identify factors that potentially determine the trends of observed changes using a molecular epidemiological analysis of the main characteristics of the epidemic process of a new coronavirus infection (COVID-19). Materials and methods. For the analysis, the data of Russian national genome sequence database of SARS-CoV-2 virus (VGARus) were combined with information on morbidity and mortality presented at the official internet resources стопкоронавирус.рф and Yandex DataLens, the dynamics of vaccination, COVID-19 disease incidence and hospitalization from the portal Gogov.ru. A multicentre retrospective observational epidemiological study was conducted to examine the sex and age structure of hospitalised patients. Anonymized case histories of patients with COVID-19 collected at different follow-up periods in the institutions of Moscow (41,561 cases) served as a source of data for the sex and age structure analysis. Results. We identified 11 periods with significantly different complex epidemiological characteristics. A decrease in the incidence among young people of working age during the period of restrictive measures was revealed. In 3 out of 11 worsening of the epidemic situation coincided with the beginning of the circulation of a new genetic variant of the pathogen COVID-19 (variants Wuhan, Delta, Omicron). A decrease in the incidence in the summer period was noted, regardless of the circulating genetic variants. Conclusion. A significant part of the observed dynamics of the characteristics of the epidemic process in Moscow can be explained by the properties of the pathogen, seasonality and dynamics of magnitude of the herd immunity. The influence of the dynamics of the herd immunity indicators on the course of the epidemic process is to be studied further.