Growth performance and immune responses of pigs from nursery to grower-finisher phase following different PRRSV-2 vaccination strategies: Evidence supporting a prime-boost regimen under field conditions in Korea.

This study evaluated the efficacy of various vaccination strategies against porcine reproductive and respiratory syndrome virus type 2 (PRRSV-2) in terms of growth performance and immune responses under field conditions at a commercial swine farm in Korea. A total of 80 pigs was randomly assigned to 1 of 4 groups: VacL (modified live vaccine), VacK (inactivated vaccine), VacLK (modified live vaccine followed by an inactivated vaccine), and UnVac (unvaccinated control). Assessments included clinical signs, blood PRRSV RNA levels, PRRSV-specific interferon-gamma-secreting cells (IFN-γ-SCs), ELISA S/P ratios, neutralizing antibody titers, and growth performance. The VacLK group showed superior growth performance compared with the other groups. At 84 days post-vaccination, blood PRRSV RNA levels were significantly lower in the VacLK group than in the VacL, VacK, and UnVac groups, whereas PRRSV-specific IFN-γ-SCs and ELISA S/P ratios were highest in the VacLK group. These results indicate that a combined vaccination strategy effectively enhanced cell-mediated immune responses, suppressed viral replication, and improved growth performance under field conditions. This study provides valuable evidence supporting optimized PRRSV vaccination strategies for commercial swine production.