By Jeremy Cooke
BBC Rural Affairs correspondent
Chief veterinary officer Debby Reynolds has announced the government decision not to vaccinate any animals, despite the latest foot-and-mouth outbreak.
The virus has been found at three Surrey farms in the latest outbreak
How would a vaccination work?
Vets use the foot-and-mouth vaccine to stop the spread of the disease. They operate in rings or zones surrounding an outbreak and vaccinate all susceptible stock in that zone.
The idea is to create a sort of "fire break", to isolate the outbreak inside the ring so it can be contained and eradicated.
What's the argument for it?
The argument for vaccination is that it can slow down or stop the spread of foot-and-mouth disease.
It is especially useful when vets fear an outbreak is getting out of control and is moving too fast for simple culling of animals to be effective.
Even if it does not stop the disease it can slow the spread sufficiently to allow the culling operation to catch up.
What's the argument against it?
Even if vaccination is used, often animals have to be culled anyway.
This is because the vaccination does not cure stock with foot-and-mouth disease and often it can be difficult to establish easily which individual animals are infected.
What are the cost and practical implications?
There are no major cost or practical implications standing in the way of vaccination.
Under the government's foot-and-mouth contingency plan, a team of vets is placed on stand-by immediately there is a new outbreak of the disease.
In the current situation that team is ready to move into the disease zone as soon as they receive orders.
What do other countries do?
Some - especially in the developing world - may simply live with foot-and-mouth disease. Others, such as Holland, use the "vaccinate and cull" system.
In the outbreak of foot-and-mouth in the Netherlands six years ago thousands of animals were vaccinated but all were later killed. In the UK the preferred policy is to rely on culling to eradicate the disease.
Can vaccinated animals still spread the disease?
Yes. But vets say that vaccination helps to "dampen the shedding of the virus". In other words it helps slow the spread from infected animals.
How could vaccinating affect exports?
It's not good.
The World Organisation for Animal Health has three categories for countries regarding foot-and-mouth.
Firstly, foot-and-mouth present with or without vaccination. Secondly, foot-and-mouth absent with vaccination. Thirdly, foot-and-mouth absent without vaccination.
It is the third category which is best for exports and that is what the UK government would like to maintain.
What does Defra say?
Defra says its vets are ready to vaccinate if needed. But they say the risk of spread outside the immediate area of the outbreak is not great. Consequently, no cull yet.