Answered by: Tomasz StadejekPublished on: July 21
Vaccination of 8 weeks old pigs can protect them against PRRS until slaughter. However it is very important to remember that the protective immunity against PRRSV develops slowly and it takes at least 4 weeks, or longer.
So, pigs vaccinated at 8 weeks of age should be protected against the challenge at least until 12 weeks of age. Even then vaccinated pigs can get infected. The level of cross protection of a given vaccine and a given wild type strain can be different. The same vaccine can have different efficacy in different farms.
However, even if the cross protection against the infection with filed PRRSV is not ideal, it is usually sufficient to protect against clinical disease caused by the infection and limits virus shedding.