Eleven more people have died from flu across the UK, taking the total to 50, the Health Protection Agency said today.

Of these, 45 died with swine flu and five with another strain, flu type B.

The deaths are mostly among children and young adults, with five cases in the under-fives and eight cases among those aged five to 14.

Another 33 cases are in people aged 15 to 64.

The figures come as some hospitals have been told to cancel operations to make way for the most seriously ill flu patients.

The NHS is preparing to expand the number of beds available for a highly specialised treatment, which is often seen as a last resort.

Extra corporeal membrane oxygenation (ECMO) helps patients whose lungs or heart are not working normally and uses an artificial lung to oxygenate blood outside the body.

The main ECMO centre is based at Glenfield Hospital in Leicester but seven UK hospitals in total are currently running ECMO beds.

As of Christmas Eve, 22 ECMO beds were in use across UK, up from five in early December.

Four more beds are now being arranged. Steps are also being taken to expand this number by cancelling planned operations at some hospitals that provide ECMO.

This will free up cardiothoracic (heart and lung) surgeons and their teams to move across to ECMO, which uses similar skills.

Other hospitals which have specialist respiratory centres and provide intensive care have also been asked to cancel planned operations.

This will ensure that those patients who are stable enough to leave ECMO can move into intensive care beds.

If all ECMO beds become full, plans are in place to expand capacity even further.

A spokeswoman for the National Specialised Commissioning Team said: "This very specialist, high risk, procedure is being provided by highly trained specialists at seven hospitals.

"The NHS continues to monitor the situation carefully and we are taking further steps to increase the number of beds available.

"For instance, hospitals providing respiratory ECMO have been asked to take appropriate measures, including postponing planned cardiac surgery, in order to maximise capacity for patients needing ECMO.

"Hospitals which have specialist respiratory centres are also being requested to suspend elective surgical work, that requires ICU (intensive care) support, to ensure capacity is available for the repatriation of stable patients from the national ECMO service.

"In addition new advice was issued to the NHS before Christmas to ensure there is additional capacity if all nationally designated ECMO beds are in use."

The spokeswoman said ECMO is "only used as a matter of last resort in exceptional cases".

Strategic health authorities (SHAs) have been asked to identify appropriate cardiac surgery centres (whose staff do not normally provide ECMO) which may be asked to provide a limited ECMO service.

Earlier today, further details emerged of people who have died from flu.

Among them is 32-year-old Sarah Applin, of Thurston, Suffolk, who died following swine flu complications two weeks after giving birth to a son.

Staff said Mrs Applin died at West Suffolk Hospital in Bury St Edmunds on Tuesday.

Her parents, Jane and Barry Waterman, said: "Our daughter ... sadly died ... of complications with pneumonia following treatment for swine flu.

"We would like to strongly urge any person on the at-risk register, especially pregnant woman, to have the flu vaccination."

Family members said Mrs Applin gave birth to son William by Caesarean section on December 22.

Mrs Applin and her husband Richard also had a four-year-old daughter.

Another woman, 45-year-old Julie Roberts, a school attendance worker from Liverpool, died on Monday.

Mother-of-two Hilary Robinson, 37, from Ormskirk, Lancashire, died on Christmas Eve of complications understood to be connected to the illness.

Ms Robinson, a hairdresser, had gone to the walk-in centre at Ormskirk Hospital around midday on Christmas Eve. She was then taken to Southport Hospital where she later died.

The Government has admitted that some parts of the country are suffering shortages of flu vaccines.

Suppliers have been asked to contact their factories in Europe for a count of UK-licensed vaccines after the Government admitted it was considering bringing in supplies.

There is no central stockpile of seasonal flu vaccines, which are ordered every year by GPs and delivered to surgeries.

The Department of Health has insisted there is "no national shortage" but admitted some areas were experiencing "local supply issues".

A spokeswoman for the Scottish Government said there were "no supply issues" in Scotland.

According to the UK Vaccine Industry Group, 14.7 million doses of flu vaccine have been delivered across the UK, with 4% of those stocks going to private companies.

The Countess of Chester hospital, in Chester, appealed to the public not to visit unless "absolutely essential".

It is also reviewing its surgery schedules and telling people with appointments for operations to await confirmation.

A spokesman said: "The Countess of Chester Hospital, like all hospitals in the North West region, is currently experiencing increased admissions due to winter pressures and influenza.

"In order to reduce the risk of patients and staff becoming ill, the Trust is appealing to the public not to visit the hospital unless it is absolutely essential. This is a precautionary measure to protect the wellbeing of patients and staff.

"The Trust wishes to stress that it is currently not adopting a restricted visiting policy but prior arrangements with the nurse in charge is encouraged to determine whether or not visiting is absolutely necessary.

"Due to emergency admissions taking priority, any patients who have a planned admission for surgery within the next week will be contacted to confirm whether or not their surgery is going ahead."

The hospital said potential visitors should call the switchboard on 01244 365 000 to speak to the nurse in charge on the ward for advice on visiting.

Professor Dame Sally Davies, the interim chief medical officer for England, confirmed the Government would be releasing leftover stocks of last year's swine flu vaccine for those GP surgeries which have run out of seasonal flu vaccine.

Some 12.7 million doses of GlaxoSmithKline's Pandemrix swine flu vaccine are still held centrally by the Government.

She said: "We are hearing some stories of the (seasonal flu) vaccine being in one place and the patient being somewhere else.

"The data we have suggests there should be enough in the system.

"Now, this afternoon, I'm writing to GPs to tell them that they can start using H1N1 vaccine on clinical need and to advise them about how they can access this and order it."

She said primary care trusts (PCTs) could order stocks on behalf of GPs.

"The message to the public is if they need the vaccine because they are in an at-risk group, they should come forward because we have it in the system."

The swine flu vaccine has a shelf life until the end of this year.

Although it will not offer protection against all strains of flu circulating this year, it will protect against the dominant strain, which is swine flu.

The NHS is recommending that people who had the swine flu vaccine last year still come forward for this year's seasonal flu vaccine if they are in an at-risk group, to ensure they are protected against all strains.

Professor David Salisbury, director of immunisation at the Department of Health, said GPs order stocks of seasonal flu vaccine every year based on estimates of how many people will come forward for the jab.

He said he did not believe that the addition of pregnant women into this year's vaccination programme had led to the shortages being reported.

There are no plans to allow healthy children to get any of the vaccines, based on advice from the Joint Committee on Vaccination and Immunisation (JCVI), he added.

Prof Salisbury insisted the swine flu jab would offer good protection.

"They are not getting a second-class vaccine," he said. "They are getting an effective vaccine and a safe vaccine which will protect them against H1N1, which is the dominant strain at the moment."

He admitted the Government had no idea exactly how much seasonal flu vaccine had already been given to people and how much may be left over in the system.

He said the ordering by GPs was based on an estimate from previous years but was believed to be sufficient to meet demand.

Figures out today showed the rates of patients presenting to their GP with flu or flu-like illness has dropped in England, although this is largely affected by surgeries and schools being closed over the Christmas period.

Nevertheless, it is thought that rates of flu could be levelling off - although numbers are currently difficult to interpret.

The number of people in critical care beds in England has dropped slightly to 783, with 30 of those aged under five, 17 aged five to 15 and 640 aged 16 to 64.

Hundreds of thousands more people searched the NHS choices website for information on flu in the last three months of 2010 compared with the previous year.

Some 50,000 searches were made, compared to just 3,800 in the same period in 2009.

Other data suggest that only around a fifth of NHS workers have had the flu jab despite being offered it.

NHS chief executive David Nicholson said more patients were being referred for ECMO than last year.

Professor Ian Jones, from the school of biological sciences at the University of Reading, said the number of people reporting flu was not unusual.

"No one knows where they will go from here but the expectation is that they will peak and decline."

Dr Tarit Mukhopadhyay, from University College London, said more seasonal flu vaccine could not be produced because there is a time lag of six months.

"The flu vaccine is still primarily produced in chicken eggs, which means there is a significant lag time to prepare the vaccine.

"This year, manufacturers folded the H1N1 (swine flu) strain into the seasonal vaccine in order to deal with the predictable increase in seasonal swine flu cases.

"It would seem, however, that errors were made in not ordering enough vaccine from the manufacturers, correctly identifying the 'at risk' groups and deciding to drop the flu jab ad campaign."

Ian Jones, professor of virology at the University of Reading, said: "Seriously ill individuals are being hospitalised at a rate that is placing the provision of intensive care beds under extreme pressure.

"While a seasonal vaccine is available, stocks are limited and immunisation is advised only for those at particular risk of a serious outcome."