Relevance. Uncertainty and inconsistency of information related to the new coronavirus infection resulted in distrust in vaccination among population of different countries worldwide. Intention: To clarify attitudes to vaccination and some reasons for refusing vaccination during the COVID-19 pandemic among military personnel. Methodology: 536 male military cadets of the university, who voluntarily underwent vaccination against COVID-19 as recommended by military authorities, were anonymously surveyed. The average age of the respondents was (21.5 ± 4.5) years. Two groups of cadets were formed: Group 1 (n = 465) with I and II category of fitness for work and Group 2 (n = 71) with III category of fitness for work according to professional psychological selection. The results were checked for the normality of distribution. Similarities (differences) in the answers between groups were assessed using χ2 criterion. Results and Discussion. A survey of military cadets revealed that professional psychological selection contributes not only to the effectiveness of professional training, but also to adherence to vaccination against COVID-19. If, according to the Russian Public Opinion Research Center, 55% of Russians have a positive attitude to being vaccinated against COVID-19, such persons amounted to 91.6% (p < 0.001) among cadets assigned to categories I-II and to 47.9% among those assigned to category III of fitness for work based on professional psychological selection. Up to 4.7% of cadets in Group 1 and 29.6% in Group 2 (p < 0.001) mentioned possible early complications during vaccination, for example, being affected by COVID-19. The authors of the vaccine also claim a small percentage of possible complications in the early post-vaccination period. In this regard, the answers of the cadets in Group 1 are quite consistent with the opinion of the scientists and developers and indicate the validity of the studies. Conclusion. Increased anxiety in a situation of uncertainty during the COVID-19 pandemic can be overcome by timely informing the public about vaccine effectiveness and contraindications by medical professionals.