Sera from the calves in group 1 (C1-C3, black bars, control), group 2 (C4-C6, red bars, vaccinated with rSFV-FMDV-P1-2A-mIRES-3C on PVD 0 followed by empty capsids on PVD 14) and group 3 (C7-C9, blue bars, vaccinated with empty capsids on PVD 0 followed by rSFV-FMDV-P1-2A-mIRES-3C on PVD 14) were collected during the experiment 3. All animals were challenged with FMDV on PVD 28. Samples from PVD 14 (A), PVD 28 (B) (prior to challenge) and PVD 36 (C) (post challenge) were assayed for the presence of neutralizing anti-FMDV antibodies using VNTs. Results were calculated as reciprocal VNT titres and are displayed as log2 values. VNT titres ≤ 11 (log2 11 = 3.459) are considered negative while titres ≥45 (log2 45 = 5.492) are considered positive. Intermediate titres are considered as inconclusive (indicated within grey bar).