Experimental reproduction of severe disease with HP-PRRSV isolates and virus derived from HP-PRRSV clones demonstrated the causal role of this virus. Recently, partial heterologous protection has been reported for Type 1 and Type2 attenuated PRRSV vaccines against challenge by different Chinese HP-PRRSV isolates providing some hope for reducing economic loss. This paper reports the efficacy of a commercially available Type 2 attenuated vaccine in young pigs against heterologous challenge with a Chinese and Vietnamese HP-PRRSV isolate. When compared to unvaccinated pigs, vaccination decreased the length of viremia and viral titer, diminished the time of high fever and reduced macroscopic lung scores following homologous and heterologous PRRSV challenge. These results demonstrate the potential use of vaccine as an aid in the control of HP-PRRSV outbreaks