Objective In emergency situations where simultaneous immunization by multiple vaccines are required,how to rapidly evaluate the effect of combined immunization is an urgent issue that needs to be solved.This study aimed to investigate the po-tential role and application value of the phenotypic changes of macrophages in rapid evaluation of the effect of combined Yersinia pestis and Brucella bovis vaccine immunization at early stage.Methods Y.pestis and B.bovis vaccines were injected into mice alone or in combination to establish animal models.The changes of the macrophage phenotypes(M1 or M2 polarization)and the CD8+T cell pheno-types and functions were detected in the early(4 d)and the late(14 d)stage of the immunization,respectively.The effect of the immuno-phenotype of macrophages at early stage on the function of CD8+T cells at late stage was analyzed.Results The co-immunization by Y.pestis and B.bovis vaccines led to the attenuation of the M1-polarization of macrophages at early stage,which were marked by de-creased expression of CD16/32 and increased expression of Detectin-1 on cell surface as well as decreased expression of IL-12 and in-creased expression of IL-4 inside the macrophage,in comparison with single vaccine groups,suggesting an interference between the two vaccines.Meanwhile,the activity of CD8+T cells(including the ratio of CD8+CD69+T,CD8+IFN-γ+T and CD8+GranzymeB+T cells) in combined immunization group showed similar tendency to the attenuated phenotypic M1-polarization of macrophages. Conclusion The phenotype of macrophages at the early stage of the co-immunization by Y.pestis and B.bovis vaccines showed consistency with the phenotype and function of CD8+T cells at late stage.It might give us some hint about the possibility of utilizing the phenotypic changes of macrophages to rapidly evaluate the effect of the co-immunization at early stage.