The government hopes to provide anti-flu drugs for 80% of the population.
A further 172 patients have been confirmed with swine flu in the UK, bringing the total infected to 1,164.
Of the new cases, 117 are in England and 55 in Scotland, where authorities say errors meant they previously over-estimated the number of infections.
A Department of Health (DoH) spokesman said only a minority of cases nationwide were proving to be severe.
Health experts say it is now becoming more difficult to track and predict where the virus will spread next.
The Scottish Government said the majority (42) of new swine flu cases were in the Greater Glasgow and Clyde area. The other infections happened in Highland, Lanarkshire and Lothian.
The government blamed a "procedural testing error" in a virology laboratory for wrongly labelling 11 previous cases of swine flu as positive, when subsequent tests found them to be negative.
Another false-positive swine-flu case in Lothian has also proved negative, following further tests.
Scottish health secretary Nicola Sturgeon said the high volume of tests being processed "inevitably" meant errors would occur.
But she added: "We are one of the best prepared countries in the world."
Of the new cases in England, 70 are in the West Midlands, where 299 people have now been infected.
There have been nine new swine flu cases in London and five in the South East, three in Yorkshire and Humberside, two in the North West and one each in North East and East England.
Another 26 cases in England have not yet been broken down into geographical areas.
A DoH spokesman said: "The localised cases of swine flu found in the UK have so far been generally mild in most people, but are proving to be severe in a small minority of cases.
"We are continuing to work to slow the spread of the disease and to put in place arrangements to ensure that the UK is well-placed to deal with this new infection."
Around 30,000 cases of swine flu have so far been detected in 74 countries, and more than 140 people have died worldwide.
The World Health Organization recently declared a pandemic following a sharp increase in the number of cases in Australia.
In the UK , the government now accepts that what it terms "sustained community transmission" is now taking place.
This is characterised by an increased number of sporadic cases with no identifiable link with other confirmed cases
The government estimates that the UK has enough anti-viral drugs for 50% of the population but has plans to raise that figure to 80%.