Vaccination does not prevent infection with FMD in vaccinated animals. Vaccinated animals can still get FMD, and can still carry FMD in their upper respiratory tracts for a period of time. FMD vaccines do not provide immunity against all FMD strains. There are 7 recognized strains of FMD, with many serotypes within the 7 strains. Vaccination against one only provides protection against that serotype.
Vaccination interferes with diagnostic testing.
Blood tests cannot differentiate vaccinated animals from animals that have had a case of FMD and recovered. In the end, if the country wants to eradicate FMD, they have to consider all vaccinated animals potentially infected. Countries that have FMD or vaccinate for FMD face export restrictions. Most countries free of FMD will not allow import of animals or animal products. In all likelihood, a limited vaccination program will be conducted in Great Britain.