Impact of COVID-19 vaccination on the severity of the course and outcomes of the disease in hospitalized patients in St. Petersburg

Abstract

Vaccination against infection caused by the SARS-CoV-2 virus, despite the problems of a biological and social nature, remains the main preventive measure to prevent the spread of this infection. The aim is to assess the effect of COVID-19 vaccine prophylaxis on the incidence of severe forms and deaths among hospitalized patients. A retrospective epidemiological analysis of official data on 13,778 patients hospitalized in the main repurposed hospitals of the city of St. Petersburg was carried out, of which 973 people had a fatal disease. The frequency of pneumonia and deaths among vaccinated and unvaccinated patients was analyzed. Correlation and regression analysis was used to determine the nature of the relationship between these factors. An analysis of the incidence of pneumonia and deaths in patients with different vaccination status showed their statistically significant predominance among unvaccinated patients (p < 0.05). Quantitative fluctuations in deaths in 2021–2022 were established due to the beneficial effect of preventive vaccinations against COVID-19, expressed in a decrease in hospital mortality rates. The greatest reduction in mortality was achieved in the group of vaccinated patients in the absence of pneumonia. The risk of adverse outcomes was highest in the presence of pneumonia and the absence of vaccinations. A significant favorable factor was the vaccination coverage of hospitalized patients. COVID-19 vaccine prophylaxis has a positive effect on both the severity of this infection and its outcomes. However, a critical factor in this case is the degree of immunization of the population.