The comet assay or single-cell gel electrophoresis has developed into one of the standard techniques for determining DNA damage, with applications in genotoxicity testing, molecular epidemiology, as well as basic studies on DNA damage and repair. The Comet assay was used to evaluate the effect of veterinary vaccines on Peripheral blood cell lymphocytes under alkaline conditions, and it was discovered that the method's ability to separate cells with different classes of DNA damage based on tail moment (TM) value was possible. The aggregation and classification  of cells in accordance to TM value revealed that in control cultures 100% of cells have been undamaged (TM<2), additionally on those dealt with 25 , 60 and 100ul/ml of inactivated  vaccines No 1 – against Newcastle, infectious bronchitis , infectious bursal  disease and turkey rhinotrachities viruses  ; No 2 – against avian influenza H5N2 virus; No 3 – against avian influenza H9N2; No 4 – against Newcastle disease virus ; No 5 – against Newcastle, infectious bursal disease and Egg drop syndrome viruses  ; No 6 – inactivated vaccine against Reo virus; 100% of comets had TM values <2 indicating undamaged DNA. The classification of comets, in accordance to tail DNA% revealed that, the DNA damage in the control group's cells was categorized as low (5–25%). Low levels of damage were seen in lymphocyte cell cultures (5–25%) exposed to 25, 60 and 100ul/ml concentrations of in activated vaccines No 1 – against Newcastle, infectious bronchitis, infectious bursal and turkey rhinotrachities viruses; No 2 – against avian influenza H5N2 virus; No 3 – against avian influenza H9N2; No 4 – against Newcastle disease virus; No 5 – against Newcastle, infectious bursal and Egg drop syndrome viruses; No 6 – inactivated vaccine against Reo virus. The experimental work carried out has allowed us to recommend comet assay for the evaluation of the biological safety of inactivated veterinary vaccine preparations.