Longevity of antibody and cytokine responses following vaccination with high potency emergency FMD vaccines.

The ability of high potency emergency foot-and-mouth disease (FMD) vaccines to promote sustainable immune responses in sheep and pigs following a single application was examined. All vaccine formulations induced a rapid seroconversion in both species, as expected, which was maintained at near peak titres for up to 6 months in sheep and 7 months in pigs. The Montanide ISA 206 formulation gave the best results in sheep. Vaccinated pigs challenged with homologous FMDV were protected from disease at 7 months post vaccination. Systemic levels of cytokines IL-6, IL-8, and in some pigs IL-12, increased following vaccination and were often maintained at an increased level for the duration of the trials. These initial results suggest that high potency vaccines may promote longer lasting immunity than the conventional lower potency vaccines in ruminants and a comparable response in pigs. Results indicate that in an outbreak situation, should emergency vaccination be done with these high potency vaccines, protection should be conferred for a long enough period for the outbreak to be brought under control without the need to revaccinate. Given the increased interval for re-vaccination the use of high potency vaccines for routine prophylactic campaigns could provide a more cost-effective and efficient means of maintaining herd immunity and is an area thus worthy of further examination.