Efficacy of a modified-live virus vaccine in pigs experimentally infected with a highly pathogenic porcine reproductive and respiratory syndrome virus type 1 (HP-PRRSV-1).

•The emergence of HP isolates represents a main concern for the PRRS control.•The PRRSV-1 DV vaccine provided partial protection against the HP-PRRSV-1 PR40 strain.•Cellular immunity was recalled in vaccinated-PR40 infected pigs after infection.•Vaccinated pigs mounted a rapid and boosted VN-Ab response after challenge.•The vaccine induced adaptive immunity which counteracted the heterologous HP strain.