Immunogenicity studies of foot and mouth disease vaccines at different concentrations of antigen and saponin.

Frenkel-type monovalent O1 and C vaccines were tested for immunogenicity under field conditions, in a large cattle farm. Both vaccines were applied in four dilutions, to furnish different concentrations of antigen, and each dilution was tested with 4 and 8 mg/dose levels of saponin, and without adjuvant. In adult multivaccinated already one eight of the standard bovine dose of both preparations developed a satisfactory booster effect, and presence or absence of the adjuvant played little role. In the growing (5-7 months old) primary vaccinated immune response to vaccination depended on the applied dose of antigen; the higher the latter, the firmer immunity was developed. The immunogenicity-enhancing effect of saponin, too, was more pronounced in the young than in the adult vaccinated. The result of the immunization was significantly improved by the use of 8 mg saponin per dose, compared to that found with 4 mg or no adjuvant in the vaccine. The best vaccination results were obtained on combination on the highest antigen conentrations with 8 mg saponin/dose. The type O1 antigen proved to be about half as strong, as the type C one, having elicited the same degree of immunity as C in a roughly double dose.