Evaluated the immune efficacy of a bivalent inactivated vaccine against post-weaning multisystemic wasting syndrome and mycoplasmal pneumonia of swine.

PMWS and MPS are severe respiratory diseases in piglets, causing developmental disorders and significant economic losses. The conventional approach to control these diseases relies on separate immunization with individual vaccines, which is time-consuming, labor-intensive, and may induce stress reactions. The aim of this study was to evaluate the immune efficacy of a bivalent inactivated vaccine containing the clinically isolated Mhp Q strain and purified PCV2 Cap VLPs. Thirty-five Changbai piglets were randomly divided into seven groups (n = 5, per group): A (bivalent inactivated vaccine with PCV2 challenged), B (bivalent inactivated vaccine with Mhp challenged), C (commercial PCV2 vaccine with PCV2 challenged), D (commercial Mps vaccine with Mhp challenged), E (sham-vaccinated with PCV2 challenged), F (sham-vaccinated with Mhp challenged), and G (sham-vaccinated with sham challenged). The immune efficacy results demonstrated that 5/5 protection with bivalent inactivated vaccine and 4/5 protection with commercial vaccine against PCV2 challenge, which was consistent with the serology results. The pneumonia lesion scores result demonstrated that the immune protection effect provided by the bivalent inactivated vaccine was comparable to that of the commercial Mps vaccines. Furthermore, the overall clinical trial results indicated that the bivalent inactivated vaccine was safe and controllable, with no adverse reactions observed in both age-matched and non-age-matched pigs. Following immunization, the pigs exhibited significant resistance to infections with both PCV2 and Mhp, reflecting a robust immunoprotective capacity. Collectively, these results support the bivalent inactivated vaccine as a safe and effective strategy for preventing and controlling PMWS and MPS, with promising potential for further clinical development.