Today, in an era of abundance of unreliable information and “fake news”, increasing social conflicts and instability, falling solidarity and atomization, society more than ever needs to establish social ties based on trust. The healthcare system is no exception. In the era of global pandemics and the growth of the anti-vaccination movement, which threatens the achieved successes of vaccine prevention, mutual trust at all levels between recipients of medical services and representatives of the healthcare system is important. The monograph summarizes the authors’ long-term experience in studying loyalty within the framework of medical and sociological research, including data from a number of scientific and analytical works that were not publicly available at the time of publication. The authors hope that the monograph will be of interest to both applied and academic specialists interested in the topic of loyalty of healthcare workers.