The protective effect of swine influenza bivalent inactivated vaccine (H1N1 AH strain+H3N2 JS strain) on the epidemic strain of swine influenza virus was evaluated in the present study. Healthy susceptible piglets aged 4 to 5 weeks were immunized twice (with an interval of 2 weeks). Two weeks after the booster immunization, blood samples were collected and tested for HI antibody levels using vaccine strains SW/AH/17, SW/JS/17, as well as epidemic strains SW/GD/21 and SW/SD/22. Then, two weeks after the booster immunization, epidemic strains SW/GD/21 and SW/SD/22 were used for challenge. After challenge, clinical symptoms were observed daily, body temperatures were measured, and nasal swabs were collected for 3-5 days to detect detoxification. On the 5th day, all experimental animals were autopsied to observe the degree of lung injury. The results showed that on the 14th day after the booster immunization, all piglets in the immunized group produced high levels of antibodies against H1 and H3 subtypes, but the antibody levels detected against the epidemic strains were 1-2 titer lower than those of the vaccine strains. After challenge with the epidemic strains, except for one piglet in the SW/GD/21 challenge group with a body temperature exceeding 40.2℃ and detoxification detected, no significant respiratory symptoms were observed in the remaining immunized piglets, and no detoxification was detected. No typical pathological damage was observed in the lungs. Compared with the unimmunized control group, the immunized piglets after challenge with the epidemic strains showed reduced respiratory symptoms caused by swine influenza virus infection, blocked continuous detoxification to the outside world, and significantly reduced pathological damage in the lungs. The study results showed that the swine influenza bivalent inactivated vaccine (H1N1 AH strain + H3N2 JS strain) can provide good protection against both H1N1 and H3N2 epidemic strains.

To Cite This Article: shen C, Chen C, Tian C, Zhang Y, Yan X, Lu W, Xu C, Shi Y and Su W, 2025. Evaluation of the protective efficacy of swine influenza bivalent inactivated vaccine against epidemic strains of H1N1 and H3N2 swine influenza viruses. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.299