Observations on the stability of foot and mouth disease vaccine antigens

The 146S particle of the foot and mouth disease virus which is used as a vaccine antigen was found to be relatively stable when stored for prolonged periods at 4 degrees C. However, stored antigens of virus strains of the SAT serotypes but not of a virus strain of the type O serotype became less thermostable at 37 degrees C following 4 degrees C storage. Vaccines returned from the field 10 months after they were made were shown to contain significant amounts of 146S antigen of the O, A, SAT 1 and SAT 2 serotypes. Vaccine containing antigens at least 6 months old was shown to stimulate an acceptable immune response.