Purpose - to compare the clinical and epidemiological characteristics of coronavirus infection (COVID-19) in inpatients during the third wave of the disease with previous outbreaks, to study the course of COVID-19 in children depending on the predicted variant of the virus and timely prevention of possible disease. Materials and methods. 861 case histories of children who were hospitalized at the Kyiv City Children’s Clinical Infectious Diseases Hospital (Kyiv, Ukraine) were analyzed for coronavirus disease during three outbreaks of the disease. During the observation of the pandemic, the following periods were identified: 1st wave - from June to November 2020 (340 cases); 2nd wave - from February to May 2021 (190 cases); 3d - August - December 2021 (331 cases) and divided children by age into five categories: from birth to 1 month, 1-12 months, 1-5 years, 6-10 years and over 10 years. For calculations and statistical analysis, a statistical package was used using descriptive statistics methods, namely: logistic regression models were built, with the definition of Chi-square criterion, odds ratio (OR), probable interval (95% CI) and ROC-curve multifactor model with the definition of the area under the curve (AUC). The median (M), interquartile interval (IQR, 1st-3rd quartile) was also determined in the work. Fisher’s test, Mann-Whitney test and Kruskal-Wallis test were used. Results. In the analysis of the observation of the dependence of coronavirus infection in children on the period of morbidity, using the method of logistic regression models, interrelated factors were identified: D-dimer (decreased (p=0.05) indicator for 3 waves, OR=7.47 (95% CI: 0,56-1)); radiological changes (decreased risk (p=0.005) during 3 waves, OR=1.66 (95% CI: 0.0009-2.86)) and procalcitonin (increased risk of elevated procalcitonin levels (p=0.07) during 3 waves, OR=4.27 (95% CI: 0.41-4.5)). Conclusions. The third wave of COVID-19 was characterized by a more severe course and a higher incidence of complicated cases (p<0.001). Among hospitalized pediatric patients, the proportion of patients with concomitant pathology progressively increased (p=0.0005). The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local ethics committee of all participating institutions. No conflict of interests was declared by the authors. Key words: coronavirus infection, COVID-19, children, incidence wave, complications.