A new paper from the University of Minnesota shares strong experimental evidence that vaccination influences PRRSV-2 evolution and can drive genetic changes that result in viral populations distinct from the original challenge virus. Vaccinated animals harbored viruses that were more genetically diverse and distinct from the parent virus. However, even though viruses diversified more in vaccinated pigs, they were present in much lower quantities, so their transmission potential in vaccinated pigs is unclear under field conditions.
Key findings
- Greater genetic divergence was observed under vaccine pressure
- Distinct viral populations emerged in vaccinated groups
- Lower viral loads in vaccinated pigs
Source: National Hog Farmer, August 12, 2025. Link. The authors concluded strategic vaccine application combined with robust biosecurity and ongoing viral surveillance offers the best approach for disease management.
While vaccination remains essential, comprehensive farm practices are crucial to prevent emergence of novel PRRSV-2 strains that could evade current control measures.”