ABSTRACT
Background: The coronavirus infection (COVID-19) pandemic has seen a progressive increase in childhood morbidity worldwide. Continuous mutation of the SARS-CoV-2 virus causes the wave-like course of the COVID-19 pandemic, which is characterized by an undulating course and the predominance of different variants of the SARS-CoV-2 virus. There are many reports that the clinical picture may vary depending on the circulating strain of the virus [7-11, 13-16]. Based on this, we decided to analyze and evaluate the presence of a pattern between the clinical and epidemic COVID-19 characteristics and the strain of the SARS-CoV-2 virus prevailing locally. The aim of the work: To study the effects of various strains of SARS-CoV-2 on the clinical and epidemiological characteristics of pediatric patients; to determine the regularity between the severity of the disease and the circulating strain of SARS-CoV-2. Materials and methods: A retrospective analysis of 945 case stories of COVID-19 disease in children who were hospitalized at the infectious diseases hospital (Kyiv, Ukraine) in the period from June 2020 to February 2022 (corresponding to a period of four waves of different SARS-CoV-2 strains). We investigated epidemiological and clinical features, as well as laboratory and instrumental parameters, comparing four waves of the disease. Results and Conclusions: A regularity between the wave of COVID-19 and the severity of the disease was found. The third wave seemed to be the most severe, due to the increase in the frequency of complications, concomitant pathology, clinical symptoms and the level of mortality. The timing of this outbreak matched with the circulation of the SARS-CoV-2 delta-variant and correlated with an increase in hospitalization rates in Ukraine.