Comparative characteristics of live and inactivated vaccines against salmonellosis in animals

Abstract The aim of this review was to summarise data on the clinical efficacy, immune responses, and epizootiological significance of live and inactivated vaccines against salmonellosis in animals. The methodology included the systematic selection and qualitative assessment of 25 publications issued between 2014 and 2025 and retrieved from international and national scientific databases. The inclusion criteria were direct comparison of vaccines; the presence of control groups; and quantitative data on clinical status, humoral and cellular immune response, and bacterial shedding. The results showed that live vaccination significantly reduces the frequency of clinical signs: diarrhoea – 15.3%, hyperthermia – 12.1%, depression – 10.2%, and reduced appetite – 9.8%, with fewer local reactions. The level of specific antibodies by optical density reached 0.74 on day 60 after live vaccination; inactivated preparations provided a faster response – 0.67 on day 14. Cellular immunity, as indicated by the lymphocyte stimulation factor (LSC), and the titre of anti-salmonella antibodies are twice as high in animals that received live vaccine, which indicates a more pronounced and prolonged activation. The frequency of bacterial shedding in faeces on day 14 was 12.4% in the live vaccine group, compared to 24.9% in the inactivated vaccine group and 53.1% in the control group. Contamination of the skin and environment was also reduced by 2–4 times. These data confirm the high epizootiological efficacy of live vaccines in conditions of dense animal husbandry. Nevertheless, inactivated preparations remain important in schemes where the use of live forms is limited, especially in booster cycles. Inactivated vaccines are most effective when used in sheep farms that are free from salmonellosis, while live vaccines are most effective in farms that are not free from salmonellosis. A rational combination of vaccines allows protection to be adapted to specific production conditions.