Relevance. The search for informative markers for assessing the immunological efficacy of a live plague vaccine remains an urgent scientific task. The goal of the studyAims was to make a comparative assessment of the level helper T-cells activation by CD69 and HLA-DR markers, in people, vaccinated against plague, in an in vitro test, using the disintegrated by ultrasonic Y. pestis cells, grown at temperature 28 °C as a specific stimulator.Materials & Methods. A cytofluorimetric analysis of blood samples of 45 individuals vaccinated against the plague was carried out. The dependence of the result of cytological analysis of the two studied cell markers on the immunoregulatory index (IRI) of the vaccinated donor at the time of vaccination was revealed.Results. It was found that for newly vaccinated individuals, the T-helpers were more intensive and prolonged by the early activation marker, while for those revaccinated with the immunoregulatory index, at the time of vaccination more than 1.5, the more intense cellular response was by the late activation marker.Conclusions. Thus, the possibility of quantitative evaluation of the immunological efficacy of vaccination against plague, based on the identification of lymphocyte activation markers when stimulated with a specific antigen, is confirmed.