Objective: to identify the clinical, laboratory and epidemiological features of the new coronavirus (CV) infection in the provision of specialized medical care to children in the megalopolis of the Russian Federation. Methods: 674 cases of hospitalization of patients from birth to 17 years old inclusive with confirmed COVID-19 in the period from March 26 to June 26, 2020 in a children’s multidisciplinary hospital in St. Petersburg. Diagnostics of SARS-COV-2 in upper respiratory tract (URT) smears was carried out by PCR (a set of reagents for detecting RNA of coronavirus 2019-nCoV by PCR with hybridization-fluorescence detection “Vector-PCRRV-2019-nCoV-RG”). Patients underwent 4 (3; 5) repeated examinations depending on the diagnosis of the referral, as well as the duration of the convalescent virus carriage. The analysis of the severity of the course of the disease, the main clinical manifestations and their relationship with the development of pneumonia, as well as the epidemiological features of COVID-19 in children. The duration of inpatient treatment, outcomes and the need for intensive care are described. Changes in a number of laboratory parameters on analyzers made in the USA were assessed: a clinical blood test on a hematological one - Coulter UniCel (Beckman Coulter), a biochemical blood test on a biochemical one - Uni Cel DxC (Beckman Coulter), a coagulogram on a hemostasis analyzer (Instrumentation Laboratory). Results: Overall, there was a favorable course of COVID-19 in children. Intensive therapy was required only in 3.6% of cases with a total mortality rate of 0.15%, Kawasakilike syndrome was recorded in 0.3% of cases. In 1/3 of patients, prolonged viral shedding from the upper respiratory tract was detected. In children, intrafamilial infection from adults was in the lead; schoolchildren accounted for half of all hospitalizations. A distinctive feature of the new infection was mild clinical symptoms with fever and catarrhal symptoms up to 4/5 of cases, gastrointestinal symptoms - in every third patient. There were no significant differences in the severity of the disease by age. Pneumonia, diagnosed in ¾ cases by computed tomography, complicated the course in 13.1% of cases. The defeat of the lungs was accompanied by fever and dry cough, and in a more severe course: desaturation, chest pains, a feeling of insufficiency of inspiration. The age peaks of the incidence of pneumonia were revealed: at 4, 9, 12 years old and at the age of 17 years, the maximum (in 1/3 of cases). Laboratory changes were insignificant and quickly reversible. Conclusion: the course of COVID-19 in children in the megalopolis of Russia is comparable with foreign information. However, taking into account the experience of “Spanish ‘flu”, it is possible that in pediatric practice the number of severe forms and unfavorable outcomes may change in the near future, especially due to the difficulty of diagnosing Kawasaki-like syndrome and the need for a multidisciplinary approach to the treatment of such patients. Currently, the most vulnerable to the new CV are children with severe oncological, neurological and cardiovascular pathology, who have a rapid decompensation of the underlying disease against the background of COVID-19.

Objective: To describe the burden of COVID-19 in a children’s multidisciplinary hospital for two years of the pandemic, taking into account of age, severity of the disease, the spectrum of underlying conditions and the intensive care need.Methods: An assessment of 6048 cases of COVID-19 in patients under 18 years of age hospitalized from March 26, 2020 to December 31, 2021 was carried out. The diagnosis was confirmed by PCR on an outpatient basis or after hospitalization with the help of diagnostic kits registered in the Russian Federation. The features of the work of a children’s multidisciplinary hospital in new conditions, the dynamics of hospitalization, age characteristics and new coronavirus (CV) infection severity in the pandemic development process are presented. The analysis of the underlying condition’s structure depending on the severity of the disease, as well as the need and volume of therapy in the intensive care unit. The frequency and main characteristics of children’s multisystem inflammatory syndrome (MIS-C) in hospital conditions, long-term PCR positivity and its effect on the duration of inpatient treatment of children have been established.Results: The spread of SARS-COV-2 in St. Petersburg required a radical change in the work of the children’s multidisciplinary hospital. During the two years of the pandemic, four waves of hospitalization of children with new CV were revealed, differing in duration, intensity, and frequency of lung damage, but having no significant differences in the proportion of severe forms of the disease (1.7-2.8% of cases). Intensive therapy was required in 3.6% of cases, of which only 1/3 was due to the severe course of COVID-19 with a lung lesion volume of up to 100%. In 1/3 of cases, patients had risks of developing severe forms and in 1/3 – other pathology. Severe course of new CV was significantly more often accompanied by the need for respiratory support, anticoagulants and anti-inflammatory therapy. Contributing factors of severe forms and unfavorable outcomes were: pathology of the central nervous system, genetic diseases and malformations, obesity, as well as chronic bronchopulmonary pathology. Mortality in the hospital was recorded only among children with severe underlying conditions (0.1% of cases). D-MVS was registered significantly more often in boys (7 out of every 10 patients), accounting for 1.2% of cases of hospitalization of children with new CV over the entire period. Convalescent PCR-positivity in the outcome of COVID-19 was detected in 1/3 of children, significantly more often during the autumnwinter waves of the pandemic and among patients of high school age.Conclusion: New CV is gradually strengthening its position in the structure of acute respiratory pathology in children. Some of SARS-COV-2 infection cases is accompanied by extensive lung damage, as well as severe systemic inflammation independently or in the other infectious diseases structure, induction of the debut of various somatic pathology is not excluded. The presented data confirm the need for increased attention at high risk of adverse respiratory diseases outcomes children. All severe cases of COVID-19 in children require a personalized approach, taking into account the existing background diseases and possible options for the progression of the process. MIS-C should be considered as a systemic inflammatory response syndrome within the framework of an infectious disease of various etiologies, differentiated with Kawasaki disease and the debut of systemic diseases. The long-term PCR-positivity in the outcome of COVID-19 requires further study to address the need and nature of therapy in order to prevent further spread of infection in the population.