A year ago, the world heard about an outbreak of a new severe coronavirus infection in China, which later, after its rapid spread across the globe, WHO defined as a pandemic. Pediatricians, of course, expected the worst-case scenario and mass illness of the most vulnerable patients – children and people of older age groups with a new infectious disease. From the immunological point of view, everything is obvious – the new pathogen is most dangerous for those who have not yet formed a defense against it, or for those with weakened defense. But it quickly became clear that, unlike, for example, a flu pandemic, there is an unexpected situation when adults, including elderly and senile patients, become seriously ill and die, and children remain practically outside the spread of the infectious process. During a year of living «in a new reality», not only physicians, but all of humanity learned to respond to a new infectious challenge, empirically looking for possible therapeutic or diagnostic interventions and at the same time trying to plan and implement scientific research that would help shed light on the questions posed. For the first time, the international medical community united to perform serious clinical trials of drugs that were proposed for the treatment or prevention of COVID-19. As a result of actions of scientists and clinicians around the world, answers to some questions were obtained, however, most of the information on the impact of the new coronavirus on the human body, including children, is still unavailable to medical practitioners. The review presents latest data on the causative agent of the new coronavirus infection, its effect on the body of children and adults, describes peculiarities of immune response to the new virus, and outlines basic principles of managing such patients in real clinical practice.