I wasn't aware it was illegal, just not adopted as policy. The reason is that vaccinated stock cannot pass a clean health bill, because the vaccine shows up as infection.
The underlying reasons for the livestock policies are all to do with economics rather than veterinary science.
If the animals were pets, or a subsistence food source, then vaccination might make sense. But then it would also make sense just to leave them to get over it, since foot and mouth is not fatal to anything but profit margins. Animals recover in a couple of months - but with margins tight, those are the months in which fattening must happen. It only takes a small interruption to push the livestock from profit into loss-maker.
Small and large farmers have competing interests. Large farms favour mass culling, because they can absorb the loss on animals that in any event have a pretty contracted life span. Small farmers (who are arguing for vaccination) are up against it, and cling on to the vaccine solution imagining it to be a life-belt.
Mass-culling probably is the best solution (short of a return to subsistence farming). In fact, the British government's problem is that they have not killed enough, quickly enough.
The pattern of the infection so far indicates that small farmers are not reporting quickly enough, and so the disease has spread quickly through the Cumbrian hill farms around the lake district and in Wales - both areas where family farms have held on.
Europe farmers massively overproduce, and most European governments will welcome the opportunity to thin out the number of farmers and slaughter some herds - as long as they're someone else's. -- James Heartfield