Evaluation of some parameters of the COVID-19 epidemic process and the epidemiological effectiveness of the use of the Gam-COVID–Vac vaccine among employees of two medical organizations in the Moscow region

Abstract

The article presents the features of the COVID-19 epidemic process for 2020–2022 and the results of the effectiveness of the «Gam-COVID-Vac» vaccine used in employees of two different medical organizations (MO). In both institutions, the dynamics of a decrease in the incidence of COVID-19 with asynchronous periods of growth and decline of varying intensity and duration has been established. It is noted that in the regional hospital, each epidemic period of growth and decline was more intense than in a psychiatric hospital. In the studied organizations, seasonal increases in morbidity were revealed, characteristic of infections with airborne transmission, as well as an increase in morbidity in other months associated with the appearance of new variants of the SARS-CoV-2 virus. The highest proportion of COVID-19 cases was among employees of the age group from 30 to 49 years and nursing staff. In the Ministry of Defense, asymptomatic and mild forms of the disease prevailed among those who had COVID-19 and accounted for 76.5 % in a psychiatric hospital and 67.3 % in a regional hospital. The proportion of severe forms of diseases was 2.1 times higher among employees of the regional hospital. According to the results of the survey, various places of infection of employees of the Ministry of Defense were identified. In the regional hospital, nosocomial infection prevailed, in the psychiatric hospital, employees were more often infected outside the institution. A decrease in the effectiveness index (IE) of the Gum-COVID-Vac vaccine was found both in a psychiatric hospital and in a regional hospital from 12.0 in 2021 to 3.3 in 2022 and from 12.8 to 4.5, respectively, and the efficiency coefficient (CE) from 91.7 to 69.4 % and from 92.2 up to 77.9 %, respectively. Correlation coefficient between the incidence of COVID-19 and vaccination of employees with the drug «Gam-COVID-Vac» in a psychiatric hospital for 2021–2022. it was minus 0.42 %, in the regional hospital — minus 0.24 %, which indicates a negative strength of the connection and a decrease in the effectiveness of vaccination, which requires a change in immunization tactics and the need to improve the vaccine.