Effective vaccination against porcine reproductive and respiratory syndrome (PRRS) virus prior to weaning

A vaccine for protecting a porcine animal against infection by a PRRS virus, which vaccine comprises (a) a polynucleotide molecule of SEQ ID NO:

• 6 or a polynucleotide molecule that has at least 85% identity to SEQ ID NO:
• 6, wherein the protein encoded by ORF1a thereof has an amino acid sequence that contains:
• (1) one, two, three, or four of:
• an amino acid N within the amino acid sequence ANV (see SEQ ID NO:
• 9);
• an amino acid N within the amino acid sequence HNA (see SEQ ID NO:
• 12);
• an amino acid Y within the amino acid sequence WYL (see SEQ ID NO:
• 18);
• and
• an amino acid H within the amino acid sequence VHG (see SEQ ID NO:
• 21);
• and
• (2) one or both of
• an amino acid T within the amino acid sequence ATD (see SEQ ID NO:
• 27);
• and
• an amino acid C within the amino acid sequence MCQ (see SEQ ID NO:
• 33);
• and
• (3) one or both of
• an amino acid T within the amino acid sequence PTG (see SEQ ID NO:
• 36);
• and
• an amino acid A within the amino acid sequence VAK (see SEQ ID NO:
• 39);
• and
• (4) an amino acid N within the amino acid sequence FNP (see SEQ ID NO:
• 45);
• or
• (b) a North American PRRS virus encoded by said polynucleotide molecule of (a) or,
• (c) said polynucleotide molecule in the form of a plasmid, or
• (d) a viral vector comprising said polynucleotide molecule, wherein the PRRS virus is able to elicit an effective immunoprotective response against infection by PRRS virus, in an amount effective to produce immunoprotection against infection, and a carrier suitable for veterinary use, and wherein said vaccine provides pre-weaning vaccination.