The foot and mouth virus appears to be contained and is not expected to spread beyond Surrey.
A Defra briefing today confirmed no new cases of the virus have been found, despite concerns of a third outbreak at a farm near Guildford.
Chief veterinary officer Debby Reynolds said the virus appeared to have been controlled by "swift, determined and decisive action".
As such the government has no plans for a nationwide vaccination programme.
Ms Reynolds assured farmers this remains "an option" and preparations are being made to launch a programme is necessary.
She said: "The decision not to vaccinate at this stage, but to retain our full readiness to do so, demonstrates that our contingency planning arrangements are working.
"The epidemiology report indicates that infection may be contained to the Surrey area. But, these are our emerging findings, this is a developing situation and new information may come to light at any stage which changes our understanding of the outbreak."
Foot and mouth has been confirmed at two farms near Guildford and Defra is still investigating a link with the nearby Pirbright research laboratory.
There is evidence the virus escaped from either the Institute for Animal Health or, more likely, the private Merial research lab.
A 10km surveillance zone remains in place around the affected firms. Beyond the immediate area, however, restrictions on the movement of animals have been eased.
Speaking at Downing Street, the prime minister said: "We have restricted the disease to a limited area of this country. The risk of it spreading out of these areas is low if not negligible."
Gordon Brown said ministers wanted to assure people Britain is "open for business"; amid concerns the rural tourist economy could be dented by the latest outbreak.
Mr Brown said farmers will be compensated and the government is looking at what measures are available to help rural economics recover.
Compensation payments will be made to farmers within the next few days.