Thirty-nine people in the UK have now died with flu-like illnesses this winter, figures show.
All but three of them were infected with the H1N1 swine flu virus, while the remainder had influenza B, the Health Protection Agency data shows.
The figures were published as the government announced it is to re-launch an ad campaign to raise awareness of how to guard against flu.
Earlier this week GPs said cases had risen to 124 per 100,000 people.
The latest figures for Scotland, released on Thursday, showed 55 cases of flu per 100,000 - up from 45.8 per 100,000 in the previous week.
The expert committee on vaccination for the UK has decided against giving the seasonal flu jab to healthy under fives or children aged five to 15.
The independent group of experts met on Thursday and concluded there was not enough evidence to extend the jab to those age groups.
The committee said the "greatest gain" would instead be achieved in increasing vaccine uptake in the at-risk groups. Those include pregnant women and people with chronic respiratory diseases, or chronic heart, liver or kidney disease.
'First line of defence'
The HPA figures show 12 people died in the UK last week.
They also reveal that, out of the 38 cases for which information is available, 23 were people in "at risk" groups.
All except one were aged under 65, and four were under the age of five.
Only two are known to have had this season's flu vaccine.
The number of people in critical care beds in England with suspected or confirmed flu has risen to 738, up 60% on the previous figures published just before Christmas.
There are around 3,500 critical care beds in England.
Professor John Watson, head of the HPA's respiratory diseases unit, said: "We are seeing a large amount of flu circulating across the country and would urge people in an at-risk group to have their seasonal flu vaccine as soon as possible as this is the best way to protect themselves from flu this winter."
Health Secretary Andrew Lansley announced the government is to re-run the "Catch it, Bin it, Kill it" campaign via national press and radio adverts from January 1, at a cost of £1m.
He denied the government had performed a U-turn - after its previous decision not to run a vaccination campaign."They are two different things. The people we would wish to vaccinate are people in at-risk groups and over 65s who can be contacted via their GP.
"What we are launching is a quite separate thing; a message for everyone. All of us can help protect ourselves and others by good respiratory and hand hygiene."
In previous years, awareness campaigns have been launched earlier in the flu season.
John Healey, shadow health secretary, said: "Andrew Lansley made a serious misjudgement when he axed the autumn campaign to help public understanding of flu and boost vaccination.
"But I welcome this U-turn, as late in the day as it will appear to many people."
The Chief Medical Officer, Professor Dame Sally Davies, has also asked the Joint Committee on Vaccination and Immunisation to assess the current vaccination programme.
She said she would ask the JCVI - meeting on Thursday - to look at "the new data that has emerged around this year's flu season and reassure us that our policy on vaccination is correct."