Purpose - to improve diagnostics and making multisystem inflammatory syndrome diagnosis in children based on the study of the clinical course and determination of laboratory and instrumental features. Materials and methods. 15 cases of multisystem inflammatory syndrome in children who were hospitalized in the Infectious Diseases Boxed Department No.1 of the Vinnytsya Regional Children’s Clinical Hospital in 2021 were analyzed. Results. The most common symptom was fever. Gastrointestinal disorders (53.33%), neurocognitive and vegetative symptoms (86.67%) were also found in children. Arthralgias, myalgias and pains in the lower extremities were in 33.33% of children, respiratory symptoms - in 20.00% of ones. Almost half of the children had skin rashes at physical examination. Scleritis and conjunctivitis was also noted in the quarter children. Leukocytosis was detected in 8 children (53.33%) in the results of blood count. Majority of children had elevated erythrocyte sedimentation rate, C-reactive protein and fibrinogen. D-dimer was increased in all children. 46.67% of children, according to chest ultrasound had fluid in the pleural cavity up to 7-10 mm, signs of interstitial pulmonary edema, increased echo-signals along the axillary line and the consolidation zone in the middle right lung from 3 mm to 6 mm. 60.0% of children had enlarged liver, spleen, fluid in the abdomen and enlarged multiple mesenteric lymph nodes according abdominal ultrasound. Conclusions. The diagnosis of multisystem inflammatory syndrome should be made according to the main criteria. It requires differential diagnosis with a number of infectious and systemic diseases. Prolonged fever and neurocognitive symptoms were the most common symptoms in hospitalized patients. Gastrointestinal and cardiovascular disorders, skin rashes prevailed. Typical laboratory changes were elevated markers of inflammation, evidence of coagulopathy and markers of previous coronavirus infection. Significant features among echosonographic changes were enlargement of parenchymal organs and signs of effusion in the cavities. Child protection from the impact of coronavirus infection should be improved. 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 the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors. Keywords: multisystem inflammatory syndrome, MIS-C, SARS-CoV-2, children.

The main principles of specific immunoprophylaxis of COVID-19 in children and adolescents were determined based on the accumulated scientific data. It was established that only two vaccines, Pfizer-BioNTech (BNT162b2) «Comirnaty» and Moderna mRNA-1273 «Spikevax» were approved by the WHO for emergency use in children and only the first of them was approved for use in Ukraine. Both vaccines have a proven safety and efficacy profile according to the results of clinical trials. The current analysis of side effects associated with Pfizer-BioNTech (BNT162b2) "Comirnaty" and Moderna mRNA-1273 "Spikevax" vaccination indicates a favorable clinical course of local, systemic reactions and myocarditis following a vaccination with regression of symptoms in all patients. The risk of the multisystem inflammatory syndrome in children following acute infection, the potential for other sequelae of SARS-CoV-2 infection, the risk of severe disease in children with underlying medical conditions, remain compelling reasons for vaccination of children and outweigh possible risks of side effects associated with vaccination. In the context of the global shortage of vaccines in the world, immunization programs should focus on groups of highest risk of hospitalizations and deaths, according to the Prioritization Roadmap. Children vaccination against COVID-19 with risk factors, comorbidities, immunodeficiency is a priority. Before vaccinating children and adolescents at low risk of serious disease, children from high-risk groups should be actively identified and vaccinated, justifying the importance of their vaccination. Despite the widespread introduction of vaccination, appropriate preventive measures for fighting COVID-19 should be taken, including physical distancing, frequent handwashing, wearing masks. It is extremely important to maintain a high level of vaccination coverage against other infectious diseases and not to delay the planned vaccination of children. No conflict of interests was declared by the authors. Key words: vaccination, COVID-19, children.

Acute hematogenous osteomyelitis is one of the common bacterial infections in children of early age, which is accompanied by mild symptoms at the initial stage of diagnosis. The onset of the disease is usually acute with fever, intoxication syndrome, focal signs of bone inflammation and limitation of limb function. Purpose - to show the features of diagnosis and treatment of acute hematogenous osteomyelitis in an infant based on clinical observation. Clinical case. The clinical case of a child of early age with acute hematogenous osteomyelitis, who was hospitalized with complaints of an increase in body temperature up to 40°C, restlessness, swelling and hyperemia of the lower part of the right thigh and right knee joint, and movement disorders in the right leg, was presented. The general condition of the child upon admission is severe due to intoxication, hyperthermic syndromes and local changes in the right lower limb, which was in a forced position, pronation. There were no active movements in the right leg, passives ones were painful. Rotational movements in the right leg are possible, but painful. The soft tissues in the area of the right hip and knee joints, as well as the thighs, were not changed in color, their swelling was noted. Conclusions. Symptoms of acute hematogenous osteomyelitis in young children are often nonspecific. Intoxication syndrome symptoms and local changes as movement disorders in the limb in children of this age group dominate. Pain can be detected during the examination, which is clearly localized with sensitivity over the infected bone; edema may be present. Changes of complete blood count are mild, while the determination of C-reactive protein during the initial evaluation can serve as a baseline value for sequential monitoring. The sensitivity of X-ray examination at the beginning of the disease is low, radiological changes appear only 7-21 days after infection. Empiric antimicrobial therapy aimed at Staphylococcus aureus should be prescribed immediately after the detection of acute hematogenous osteomyelitis clinical signs even before receiving results of additional research methods. The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.