After first ruling it out, then in again, and then letting the matter drift for a while, it now seems that the Ministry of Agriculture considers the use of vaccination to stop foot and mouth disease very much a "live issue".

But is this an admission that - despite other recent pronouncements - the outbreak is still so seriously out of control that other measures are needed; or has this a more nakedly political tinge - that with the likely delayed election date itself moving inexorably closer, the Government now needs a breakthrough to show it is in charge?

Whatever the reason, it is certainly true that some farmers themselves now think vaccination may be a necessary last resort. The Government's chief scientific adviser Professor David King explained this re-think to the Today programme. He said "We have been actively considering vaccination all along as a supplement to our cull policy - and at this stage we're looking at the possible vaccination of dairy cattle that are currently being over wintered in sheds"

Professor King explained that vaccination under these circumstances could work - which would be vital, as these cows would be brought out to pasture, and could suddenly be exposed to the virus. But he concluded that vaccination is only an "adjunct" to the cull policy, and is not considered a major way of controlling the disease.

Agriculture minister Nick Brown, re-thinking vaccination policy

The government now says they've always had an open mind on vaccination. But in the first days of the crisis they were defiantly against such a course of action, and even three weeks in to the outbreak, Mr Brown was sending out strong signals about where he stood on the issue, as he told James Cox on the World This Weekend as long ago as March 11th.

But in the weeks since then, and as the scale of the problem became more and more evident, the Government line subtly changed. A fortnight after that interview, Mr Brown was saying that he had "a duty to consider" vaccination.

A week later his department said "vaccination may play a part". Up till then, farmers remained adamantly opposed, because of the threat to their ability to export if Britain lost its disease-free status.

But last Friday, as the carcasses mounted and as it became clear that the scale of the crisis was overwhelming the country's ability to contain it, even the NFU's regional director in the South-West, Anthony Gibson, was considering alternatives, as he told the World At One.

So what exactly does vaccination involve, why have the farmers been - up to now - so wary of it, and why is it now being more actively considered?

Government's chief scientific advisor considering vaccination

There does seem to have been some confusion about what type of vaccination was involved, and its consequences, as I was told by Britain's leading expert in the field, Professor Chris Bostock.

He's the Director of the Institute for Animal Health at the Pirbright Laboratory in Surrey, which has been doing most of the testing for MAFF and is the only place in the UK licensed to handle foot and mouth vaccine.

To hear more of the interview press on audio icon at the top of the page.

Will the use of vaccination be restricted - for example to those farmers with cattle now in winter quarters which need to be moved out to spring pastures ? That is important, for the time for them to be moved is now, but moving them increases the risk of further transmission of foot and mouth.

But others think their animals deserve equally special treatment. Will Cockbain runs a flock of Swale dale sheep in Cumbria. They are hardy little creatures, used to living on the high pasture. But they are not being considered as current candidates for vaccination - which may be a death sentence, not just for the flock but for the species.

Mr Cockbain is a deputy county chairman of the NFU and sits on the MAFF Hillfarm Advisory Committee - and he's in no doubt about what he wants for his animals. He told us that if many of the rare flocks weren't vaccinated they could be wiped out

But Mr Cockbain's fellow-farmer and colleague, Keith Twentyman, is not yet convinced that vaccination should go ahead without a lot more assurances from the Government.

He's the group secretary for the NFU in North Cumbria and he'll be meeting the Chief Scientific Advisor, David King, who's in the region this lunchtime.

He told us that he and his fellow farmers needed assurances that people would still buy their milk, and supermarkets would still buy their meat, before they even considered vaccination.

"Vaccination has always been an option. It should be seen as a complement to the cull policy, not an alternative

MAFF statement

The Minister has been canvassing farmers' views on a possible change of policy - indeed, he roped in to help him his Tory opponent, David MacLean, the MP for Penrith and the Border. As Mr MacLean told us, last Wednesday Mr Brown phoned him, and asked him how farmers were faring in his constituency.

He told us vaccination could give Cumbria "pariah status"

The Minister of Agriculture, Nick Brown, was unavailable for interview, but MAFF did issue this statement:

"Vaccination has always been an option. It should be seen as a complement to the cull policy, not an alternative. Vaccination is being considered but no final decisions have been made. Nick Brown has spoken to David McClean and to Eric Martlew MP to hear their views and those of their constituents."

To hear some of the interviews, please click on audio icons at top of the page.